While the certain stuff - like difference in efficiency/state of public infrastructure can be observed after short trips overseas, what I wanted to mention that most cases of reverse culture shock cases come in light when one spends significant - let's say more than a year - time away from home country.

To me with above mentioned expensiveness, loudness was the second thing which was very easily to spot. During dinner at restaurant we could hear a conversation at a table across the hall.

Other thing which become noticable, sorry for pointing this out - how large (or you can use your own word) people are. And that in Bay Area, which probably is not the worst case if you take US in general.