The USA is of course a big place. Two weeks is a good vacation. You'll get to see a lot. California is a prime vacation hot spot - movie stars, San Francisco, Yosemite, surfing, Tahoe, Indian/Spanish/Mexican/Gold Rush history.
I don't TA as much about other areas. I'll talk about fun things i've done. Are you set on Calif yet?
I characterize Oregon as a very relaxed and relaxing vacation with forests along the ocean, and friendly people and comfortable inns. Try the Columbia River Gorge, Three CApes Loop, MacKenzie River. ...and is great to combine with a visit to WAshington state and Victoria B.C.
Have you heard of the Four Corners area? This is where the corners of four states meet in SW US. This area is filled with the best desert landscapes we have - the Grand Canyon, Havasupai, ARches NP, Mesa Verde, Zion, Bryce, Vegas, Valley of the Gods, rafting, pertroglyphs and rock art.
Then there's New York. ...combined with some other US destination, like Washington D.C. or Chicago, Boston, New England for your two weeks, would work well.
Don't forget Hawaii and Alaska, they're in the USA too.