comparable level of difference

........................................................................ ok

I think to understand the differences you need a lot more cultural and historical perspective. As a young country the USA lacks a strong national indentity compared to a lot of European nations. Thus, when they visit another country they only look at the surface.

Here's one example of a massive factor in deciding cultural differences; historical rivalries and alliances.

http://en.wikipedia.org/wiki/List_of_conflicts_in_Europe

On the other hand, the US only fought inside itself once to my knowledge (the civil war?). In every single other war the US has fought together as one unit, always united. The "Us VS Them" mentality is "America VS for example Communism". There's nothing close to that level of cultural unity between european nations, because they're definitely different countries.