Krampus -
After 4 years in China, re-entry was HARD for me, ain't gonna lie. But I also have friends who returned to the States and readjusted quickly, with minimal drama and angst. Part of my problem was that I returned to the States, but to a different city where a knew very few people, and was dealing with being broke and unemployed.
I found
this book helpful in preparing to come home. I think the Peace Corps used it with their volunteers for a while. Not everything will apply to you (the author discusses expat businesspeople a lot) but it gave me a general idea of what to expect from people when I came home, and how weird I would appear to them.
Transitioning back is hard, but don't borrow trouble - it might be a piece of cake for you. It's hard to predict how it will be for you until you get back.
Oh, find some other former expats to hang out with/communicate with, wherever you end up! Venting and talking to other "China peeps" my first couple of years back was invaluable.