What would be one word to describe each country's tank doctrine during World War 2?

I’ll stick to the major powers in this answer when describing each tank doctrine just to keep the focus narrow.

Soviet Union: Quantity or Numbers

The Soviet Tank Doctrine rested on the use of their medium tanks in the form of the T-34 and T-34/85 in numbers. While these tanks were indeed quality tanks, they were still matched and outclassed at times by the more heavily engineered German Panzers who placed heavy emphasis on quality or quantity. The main target was to have a 5–1 advantage in numbers of tanks when engaging the German so as to wipe out their advantage in quality and effectively overwhelm any defending force. The use of the shock army concept in the Red Army relied on this very notion of numbers and strength to break defensive lines which later became the Deep Operation doctrine the Soviets would employ during the Cold War. Soviet General Konstantin Rokossovsky would use the shock armies in his wide maneuvers on the Eastern Front when he launched Operation Uranus and Operation Bagration.

United Kingdom: Combined Arms or Balance

The British learned in North Africa that they would have to adapt to a new system of armored warfare to combat the success of the Blitzkrieg doctrine that German Panzers had become successful in implementing. The chose a more balanced approach in combining infantry, artillery, and armor into a combined assault force with a heavy emphasis on a strong artillery contingent. Battles would be won with a combination of these factors rather than relying on armor solely to win engagements. British Field Marshall Bernard Montgomery would become a famed proponent of the Combined Arms approach, usually engaging in a battle only when he had a 10–1 advantage in manpower and tanks and taking extensive time to form his battle plans before an engagement.

United States: Speed or Specialization

The US is unique in the fact that it combined two forms of armored warfare doctrine to make their own. By combining the doctrine of Combined Arms used by the British with the Blitzkrieg doctrine employed by the Germans, the US was able to develop a more holistic concept of Combined Arms that gave the depth of planning that Combined Arms required with the speed of Blitzkrieg. The US would use a mixture of air support, artillery, engineers, and armor to form spearheads that would penetrate hard into specific parts of the enemy defenses while supplemental Tank Destroyers would be employed solely for the task of eliminating heavy armor. The US never expected to match the Panther or Tiger in 1 on 1 combat and opted for using tactics and speed to either outmaneuver or overwhelm German tank formations. General George S. Patton would use this combination of doctrines to help Allied forces form the Falaise Pocket and encircle over 50,000 Germans in a pincer maneuver.

Germany: Blitz or Shock

Germany had developed the concept of Blitzkrieg, which it was never officially called, during the interwar period between World War 1 and World War 2. Famed German General Heinz Guderian was a famous proponent of Blitzkrieg, opting for wide, operational level maneuvers with armored units to achieve results. These maneuvers would be accomplished with quality medium Panzers along with superior tactical support from the Luftwaffe to achieve large breakthroughs and form pincer formations within the enemy's own lines. These Panzers would be supported by mechanized infantry divisions that would concentrate on the Schwerpunkt or focal point of a defensive line for an intense push. This doctrine relied on surprise breakthroughs, lack of enemy preparation, and the inability to respond to the breakthroughs from the enemy to achieve maximum results. The push through the Ardennes Forest was probably the most famed example of how an unexpected breakthrough wreaked havoc on the forces of another nation, throwing France into disarray opening a direct road to Paris.

Japan: Afterthought or Support

Japan had used the interwar period to place a heavy emphasis on their Navy rather than their Army and the feud between the IJN and the IJA did little to help the development of Japanese armor. By the outbreak of World War 2, the Japanese were still relying on tanks such as the Ha-Go which were little more than 37mm guns wrapped in paper. They were mainly used for infantry support roles and when the war procceded to turn against the Japanese, were switched to entrenched positions. Since they never really placed any real investment into the development of the IJA or its tank corps, Japan suffered heavily at the end of the war in the face of the M4 Sherman that the US employed. General Tadamichi Kuribayashi would use what remained of the IJA tanks under his command as entrenched emplacements in his bitter defence during the Battle of Iwo Jima, being unable to match American armor in direct combat.

Each nation developed according to their own needs and employed what doctrines they thought would be the most effective. Germany, the Soviet Union, and the United States are primarily responsible for the current state of armored warfare today, their respective doctrines being modernized and adapted to the needs of an ever changing world with combined arms and shock tactics still playing an integral role.

One only need look at the First Gulf War to see how the US employed a combination of Blitzkrieg and Combined Armes principles in its “Shock and Awe” campaign when using its armor to maximum effectivness, evident in the Battles of Medina Ridge and 73 Eastings.

Doctrine of tank employment.

Forget everything else and all the answer that will say “soviet bad, crapy tanks, sent mass to die without brain, uhhh, oggghh”…

The doctrine of the Germans and Soviets were the only modern doctrine. Japan, France, UK, Italy and the US kept using WWI theories.

In Germany, Russia, France and UK was a movement of army theoreticians that saw the game changing tools that the tanks were, and more combined with the Aviation.
While in France and UK those officers and advocates of the tanks as independent combat forces, were silenced and told to shut up, in the Soviet Union and Germany they were enthusiastically heard and given room to test and develop the future of warfare.
That was specially tested in the Spanish Civil war (SCW) were different tank employment concepts were used along technology and tank concepts.

From the SCW it was very clear that slow infantry support tanks were useless and lagged behind other tank types that then had to abandon their roles to support the infantry since the other tanks were still on their way when troops made large advances.
Multi-turreted and multi-cannon was also useless, over-complex, unreliable, costly to produce, heavy and with low mobility.

Soviet Union: Their tanks were designed and organized to operate inside the Deep Battle Doctrine:

If you read that, you can see that is identical to what people call “Blitzkrieg”, a term that was made up but WWII british newspapers and the german NEVER used.
It is the same the germans used, because the theory development in both countries reached to the same conclussions, including the results of the SCW.
Thanks to sanctions and prohibitions to Germany after WWI, they developed everything in secret, and tested tank forces in the Soviet Union, in the Kama Tank school and took lessons from the soviet military.

In this doctrine, the sock forces, that will attack the enemy weak spots, are a Combined Arms Force. Independent combat tank units attacking the enemy lines and advancing to reach the enemy rear supported by heavy artillery support, air support and protection and mechanized infantry that followed them.

Later the Soviets tested in real life this against Japan, in the Khalkin Gol battle, with absolute success.

So the doctrine of employment for the soviet tanks were that, attack the enemy, break them, and keep penetrating their territory leaving weak enemy live units to be dealt latter by the advancing infantry.

So following this they designed their tanks leading to the successful BT series, T-34 series, and KV/IS series.

Soviets organized their tanks in Tank Corps. Depending the year 2/3 Tank Regiments, 1 light reccon regiment, 1 Motorized Rifled Infantry, 1 assault/antitank regiment.

True is, they had then specialized tanks to act as “assault guns” that were meant to destroy enemy fortifications. This tanks latter were employed successfully as anti tank units when the Soviets were in problems in 1941 and latter with the heavy armored Tigers, leading to the development of specialized tank hunter units (the SU-series), known in english as Tank Destroyers.

Germany: Practically the same that the russians. But with a major emphasis in crew training.
We can divide the german tank doctrine in a pre and post Barbarossa.
Initially Germany deployed tanks as the soviets. Independent attack units in a Deep Battle doctrine and combined arms operations.
Yet the Germans used 2 designs of tanks. Battle tanks with a fast velocity cannon, and support tanks, with low velocity high caliber guns. The first were meant to deal with enemy armor in their attacks and the latter follow them destroying enemy fortifications, machine gun position and give support to the mechanized infantry.
The Panzer III was the first and the Panzer IV the second.

German armored units were organized in Armored Divisions, depending the stage of the war; 2/1 Panzer Regiment, 1 Mechanized Infantry Regiment (later reinforced with more batallions per each), anti aircraft guns, towed artillery and support units.

They also used specialized assault guns for fortifications. The Stug III. Latter up-gunned and used as anti tank. And anti tank motorized cannons, like the Marder.

In the invasion of the USSR. They had to use the Pz IV to deal with the newer soviet tanks because the punny 37 mm cannon of the Pz III couldn’t penetrate it. The designed for tank combat Pz III became obsolete and the Pz IV evolved to be the war horse of the Wehrmacht and, despite its flaws and defeat, the best tank in history. It fought in all fronts and accepted lots of modifications and upgrades fighting even after WWII in the middle east.
By this point the german tank doctrine abandoned the support “derp” design and went fully for combat units a la jack of all trades. They focused then in crew protection since they had less people than the tanks they could produced, and better cannons, to deal with more enemy numbers and their increasing protection.

France: they kept their army with an structure, thinking and doctrines from WWI waiting another static war, discarding the maneuver warfare.

France fielded separated doctrines for tanks. Infantry tanks and tanks to face the enemy. Despite having the largest tank force in Europe. Most o the French tanks were included in Infantry divisions for infantry support. In battle they had poor coordination with infantry and serious problems to execute coordinated advances.
The Tank Divisions were few and despite having armor and cannon in advantage to the earlier germans, they failed in operational levels unable to keep with the employment doctrine of the Wehrmacht.

UK: The British lagged behind the Soviets and Germans in tank employment doctrines despite having realized the usefulness of the tanks.
By WWII they fielded slow well armored tanks with large cannons as infantry support tanks, the Infantry Tanks. And the Cruiser tanks, less armored, faster and with small high velocity cannons. As the french, their employment doctrine was based in WWI and couldn’t face the evolution of that day battlefields. Infantry ironically were useless for the job, as the french, but did well facing tanks thanks to their armor and guns, while the Cruiser tanks were completely useless with ineffective guns and mobility.
Latter the british improved their designs reacting to the german superiority and improving mobility, firepower and protection.

US: The US was the most primitive tank force in terms of employment doctrines. Following France, they focused on Infantry support tanks. Enemy armor had to be dealt with the aviation and artillery. This probed wrong against the German designs and warfare. Early Shermans, and M3 were absolutely useless in the roles they had been designed and had to face the German Pz III and IV with their superior guns. The poor M3 Lee was employed by the british against the german with relative success using its infantry support hull mounted cannon against the Pz IIIs, while the 75 mm of the Shermans were completely inferior. Latter the British up-gunned them with the 17 pounder.
With the time the US adopted a similar 76 mm cannon and improved armor and ammunition of the Sherman creating specialized combat tanks to face german armor.

In another side, the US decided to counter enemy armor with Tank Destroyers, the Gun Motor Carriage, that would act in similar ways to the German Tank Hunters and Soviet Anti Tank self propelled guns. But in this case, the US Army focused mobility and firepower, ignoring armor.
This units had a great development after the african campaign.

The US also experimented with dedicated Heavy Tanks to deal with the german heavy tanks. But only the M26 passed the prototype stage and none saw combat.

One of the design requirements of tanks that kept the size en weight of the US tanks is that they had to be shipped to the combat zones and use old weak european bridges or none in the pacific. That kept the heavy tanks development in cage along the fact that the US saw those tanks to expensive while they could field more Shermans and replace without problems the loses.

Japan: They were the most primitive and focused exclusively in infantry support, despite some developments.
As the US Japan had to ship their tanks to the combat zones, mostly had terrains with bad or null infrastructure. The enemies faced in their theater had no modern tanks neither and were primarily infantry.
So they doctrine was simple, infantry support tanks.

Latter they had problems facing the US light tanks with they lights high velocity cannons and then the Sherman that was superior to any Japanese tank.

Russsia - Simplicity

Germany - Quality

USA - mass-production

British Empire - thickness

Czech - cost-efficient

Romanian - non-existent

France - Logical

Japanese - LOL

Italian - LOL2

For the US I think the apprise term is .

"disposable " producing th Sh r r man long aster it had become an obsolescent Deathtrap that was commonlying called a zippy or a Ronson (light on the first drive every time" by its crews and "Tommy cooker" by the Germans.

I don't know about one word but in a few words
: Germany - powerful
Russia - good allrounder
US- easy to produce and maintain