Yeah Im thinking the difference is not so much a church thing as a community thing. How popular are non-church based community events in Europe? Block parties, big potlucks, public barbeques, community clambakes, community dances,town faires, etc.? Events that are based around interacting with the people who live around you and whatnot. All of these are staples of much of American Life and churches are one of the organizations responsible for providing venues and inviting people to come and getting the community not just attending but involved in setting things up and really feeling like they are part of the event.
Hm. That's difficult to answer. Some of the stuff you describe I'm not that familiar with.
Might have to do with the fact that it's a lot more densely populated here, our "villages" can have a few thousand inhabitants and even small villages are not very isolated, but only a few miles away from the next bigger town. So a village festival will only be popular among part of the population since there are plenty of other things to do. There are local festivities that are extremely popular, most towns have at least one, in a medium sized town there are several every weekend in summer. There are towns, clubs and other associations organizing those, religious communities are just one among many.
Oh, and while sports are extremely popular, sports are not centered as much around schools as in the US, there are no school teams, but plenty of sports clubs, which are basically their own communities.
Then pubs and night clubs are extremely important in socializing.
I guess it's mostly the "how" that is different in the US, though I'm not sure if the community aspect, the being part of the event thing, is really important to many people. Especially younger people rather find their own ways to socialize, though of course many just organize their own events.