I've been back in the USA for 5 months and thinking about cultural re-entry issues lately. A lot has been written on this over the years, but most companies and non-profits don't implement it. They offer less support for re-entry than they did preparing you for your overseas work. Our organization was much better than the average! I also enjoyed a great book, "The Art of Coming Home". But here are some quick thoughts.
1) You do weird things for a while even though you try not to. I cognitively know that most bathrooms in the USA have toilet paper, but I still carried a roll with me the first few weeks. A colleague also pointed out that I still re-confirm appointments 24 hours before the appointed time (probably out of a fear the 'monsoon' rains or an unnounced strike will come up?!).
2) You slowly remember who's who. Living overseas is all about understanding a new network and who are the influencers versus the followers. You listen or filter advice based on who it comes from. Upon return, I'm reassessing (especially in the professional sphere) which organizations or people are still on the forward edge and speak with credibility.
3) You notice odd, small changes in your home culture. The explosion of gift cards for sale immediately caught my attention upon return. The amount of postal junk mail people receive. And more.
3.5) You enjoy the small pleasures. Like snow falling this morning and the windows that seal completely. And sinking my teeth into a brownie...or a beef hotdog.