If I were visiting the US from another country, I'd probably choose to hit the Grand Canyon, then Vegas, Disneyland, Yosemite, San Francisco, Napa Valley, and maybe up to Seattle. If you have time, Austin, TX is a cool city. Chicago too. Mt. Rushmore is worth seeing, and the geysers in Yellowstone are pretty cool. Washington D.C. is a pretty awesome town.
Really if I were a non-American visiting, I'd just rent a car and take a longass road trip and just see what I run into. There's a lot out there.