This subject, while very interesting, might very well become pointless if we do not acknowledge how extremely generalizing it is.
Europe is not a country, it's a continent. Assuming any inherent European culture that should be coherent from Finland to Spain to the Czech Republic is way of base. America is two continents, but I assume the OP is referring to the USA. In that case, while this country is huge and diverse, at least the states have two things in common, namely language and government. These are significant cultural issues, and to some extent will probably mean that the USA is somewhat more culturally homogeneous than Europe.
With the advent of an international music market and the widespread use of English, some music sociologists have theorized that a Swedish hiphop fan might feel closer to the American hiphop fans than to the Swedish rock fans. I think there is some measure of truth to this, but I still believe that national and local traditions are more deeply rooted than we are usually aware of, and most likely take primacy over our musical preferences in defining our behavior.
From my experience of playing in quite a few different European countries, I have noticed some differences in the attitude of the audiences. However, while I believe I could say something useful about the differences between a German audience and an Italian audience in general, these differences always fade when compared to the differences between the audience in a small, local metal club or a large rock festival. And there is just no comparison between the turnout and the energy of a crowd on a Friday night or a Tuesday afternoon, regardless of country and probably regardless of continent as well.
Martin
