Lucas' suggestion of southern Utah is good. Look up the national parks in Utah. But, My vote for scenic Beauty goes to Yosemite Not instead of, but in addition to Utah. I'd also make sure to hit the pacific coast route - especially from about Santa Barbara CA to Astoria OR.
And Yes, the Trans AM, which I plan to do next summer, to get a great cross section of the US.
I think the Great Lakes area - say the North Lakes route would be a good addition.
If you happen to do the Southern Tier too, I'm in Mesa (next to Tempe) and on the Warm Showers list.