Is it so weird to imagine that having a shared communication space for one's neighborhood is desirable? There's a group for my neighborhood in Houston that's great for referrals (e.g., electricians), or notes about neighborhood businesses, etc. I can't imagine this idea is uniquely American, but maybe it is.

Yes, parents often participate in PTAs. Parent engagement is a big deal in education.

Yes, in many places in the US there are food trucks. People often enjoy them. Finding out where a given truck will be on Tuesday is useful!

Businesses generally keep Facebook pages in the US, usually as a supplement to a real web site, but also because Facebook has traditionally been where everyone is already.