If you plan on visiting a lot of places in a state, especially national parks and such, consider renting a car. You can get around with buses, but it is easier to drive around yourself and see all the places you want.
Eat and drink: since the States are so big, there are lots and lots of local specialties: the Philly cheese steak in Philadelphia, a hotdog on the streets in NY, the tasty texmex in Texas, the crealo cooking in Louisiana. Go and try them all when you have the chance. Have some corn bread, for Europeans it sounds like a bread made of corn, but it is more cake like. Have a dinner at a true ‘Diner’, the roadside restaurants you see in the movies. There are lots of microbreweries, you should try at least a few of the locally brewed beers.
Pick a state to visit:
Louisiana
California
Nevada
Arizona
Texas
Colorado
New Mexico
Utah
New York
Florida