I can't speak for every American but usually things like this are optional and I'm pretty happy to go if I have nothing else to do

I've only worked in Western Europe, and regular social activities in the workplace have been a common feature, across countries. Usually either as a weekly lunch outing or post-lunch activity (e.g. daily foosball or Friday timeout (beers optional)).

They were all during work hours, though.

EDIT: also, the level of "officialness" varied. Some were organized by the company, others by the direct manager of a team, and others by the employees themselves on a more personal basis.

Going to a work outing once every few months to talk to people over free beers isn't preventing me from having a life outside of work. Plenty of people skip it too.