Lots of good recommendations in the East and here are some Western ideas: Whenever I find myself on I-10 between LA and Phoenix I like stopping at the
Patton Museum. From Google I see the armor museum in Ft. Knox is also called the Patton Museum, which makes sense. Also, if you like airplanes there are some great museums in CA and AZ. The
Palm Springs Air Museum has some great WWII warbirds. Also,
Pima Air Museum near Tucson, Arizona is great and a lot more compact than the boneyard at Davis-Monthan Air Force Base, which probably has more airplanes parked in the desert than are operational in the world's air forces.
Last time I was in the States I was fortunate to hit up the Dulles Airport Air & Space Museum for the first time, which is a must see if you like airplanes at all and are in the Washington, DC area. Anyway, have a good trip. I'd love to have four free weeks in the U.S.
Edit: I once had some Swedish buddies who bought a car in New York for $500 and sold it in California for probably not much less a couple of months later. Not a bad way to see the place and cheap.
Cheers,
CC
Beer, because barley makes lousy bread.