I'm not European, so all I can do is shrug. Obviously there are tons of people in Europe and they're not all identical, but my observation is that compared to me, they're more comfortable with the inherent ambiguity of not being able to understand everything in a language, and still being able to function in that language.

I think Europeans, in general, are much more comfortable with the idea of just making due with whatever language is available, at whatever level, where as for Americans, speaking a foreign language is much more of an event, with more ego tied into it. The fear of failure is amplified, and that fear is a huge reason that more people don't try to learn.

Maybe I'm just seeing a self-selected group of Europeans who are already multi-lingual, and it's not childhood exposure at all, but my theory is that the normality of language learning in Europe is a causative factor.