As a dual citizen currently in the UK visiting family in Wale I can think of a few.

Front doors: turnable knobs are a thing now. I shouldn’t need keys to get in my unlocked house.

Plug sockets. The UK one is needlessly large. The whole world thinks this

Bread. British bread tastes like cardboard. And don’t tell me it’s because US bread is full of sugar or whatnot. It still doesn’t justify tasteless bread.

Window screens. (Not to be confused with windscreens). Not an issue right now, but what the hell? There are flies and wasps here too. I’d like to open the window in summer without letting in everything in the great outdoors.

Air conditioning. See above.

Central heating. See above.