New Mexico - Pueblo Indian have some of the most beautiful pottery in the world.
Arizona ? Grand Canyon, Montezuma, Indian historic sites (may have some Pueblo influence).
California ? Southern, LA & San Diego are 2 of the great culture centre in the US. (Disney Land, Holly Wood, Museums & Art Galleries)
Nevada ? Las Vegas.
Oregon ? Sand dune.
If you spend time near the south/west you could jump across the US/Mexican border to have some Mexican experience. And, if you pend time on the east you could do the US/Canadian tour.
I don?t know the east too well, because I haven?t spend much time there. You could pick up a copy of the Lonely Planet on the US, and it will give you a good description of the US.