The Atlantic has a great overview of guidebooks written for tourists visiting the United States, ranging from the philosophical:
Politics get heavy treatment in the books, as do the subtleties of discussing them, maybe more so than in any other guidebook I've read (what can I say, it's an addiction). Lonely Planet urges caution when discussing immigration. "This is the issue that makes Americans edgy, especially when it gets politicized," they write, subtly suggesting that some Americans might approach the issue differently than others. "Age has a lot to do with Americans' multicultural tolerance."
To the mundane:
You might say that global food cultures tend to fall into one of two categories: utensil cultures and finger cultures. The U.S., somewhat unusually, has both: the appropriate delivery method can vary between cuisines, and even between dishes, and it's far from obvious which is which. Baked chicken is a fork food, but fried chicken a finger food, depending on how it's fried. If you get fried pieces of potato, it's a finger food, unless the potato retains some circular shape, in which case use your fork. And so on. Confused yet?
On the whole, the advice is pretty good, and ranges from the hilarious (don't bring toiletries as gifts to a dinner party) to the depressing (gays and lesbians are encouraged to avoid rural areas). Kinda makes me want to go out and buy a USA guide book!