The thing that most people don't realize when they think about this scenario is that it wouldn't be like the entire full strength of the US military on one side of a field somewhere, and a bunch of rednecks with hunting rifles on tbe other. People often envision planes and tanks bombing and slaughtering underequipped guerillas by the thousands. Not only would that not be the predominant form of battle, but even if it was, the US already lost such a war in Vietnam. Air supremacy, and more explosive ordnance and napalm than was used during the entirety of WWII, killing millions of such underequipped soldiers and civilians, and the US still lost.

If the United States can lose based on negative public opinion for killing even a few hundred thousand to a million civilians in a foreign country, what do you think is going to happen if they start killing millions on tbeir own soil? They would face a constantly swelling army of enraged citizenry. The armament wouldn't even matter anymore. How can you subjugate a populace if there is no one left to rule?

If the US started using military scorched-earth tactics on their own soil, their own people, they've already lost.