How long can you drive per day? How long are you okay with spending on one place?
Some are a bit out of the way.
Death valley, meteor crater, hoover dam, grand canyon (south and north side), monument valley, bryce canyon, salt flats near SLC, yosemite, sequoia national park, kings canyon national park, sequoia national forest, other parts of the sierras, yellowstone, the tetons, craters of the moon, redwood national / state parks and forests.
I haven't even been to half of these, but I've travelled a bit in that area. A few more upcoming soon. All the ones I've mentioned and been to are worth it, the others should be as well.
The farther per day you can drive, the more time you can spend at a specific place. I recommend a couple days in Yellowstone, and a couple days in the Arizona area, and a couple days in the Sierras, though not necessarily all on one trip. Also, after Yellowstone, if you swing to the coast (past craters of the moon), you can see Seattle and Portland, but more importantly, you can choose between (or see both of) several mountains in-land, and the beautiful coastline. (Washington, Jefferson, Rainier, Hood, St Helens, and probably a few more I am forgetting.) You can then follow the coastline south, break off a bit to see redwood national / state park, and continue following the coastline. It's an absolutely beautiful drive, especially as you'll be driving on the ocean-side lane heading south.
I don't recommend seeing all of those in two weeks, you'll just be exhausted and checking things off a list. Anyways, a simple path would be Yosemite for a couple days, a quick stop by the salt flats going north, Yellowstone for half a week, then over to the coastline.