First of all, let’s try to avoid American-bashing, and stay respectful to everyone.
I’ll start: for me it’s the tipping culture. Especially nowadays, with the recent post on !mildlyinfuriating@lemmy.world with the 40% tip, it just seems so weird to me to have to pay extra just so that menu prices can stay low.
I read a travel guide to another European city I was visiting, and the guide was aimed at Americans. It’s a major really walkable city, with car access as good as nonexistent (wonderful). It surprised me, that some Americans walk so little, that the first advice in the guide was “start by trying to walk around your house”