Um Hollowfox, As I noted in the second to last sentence:

"...given your time constraints, when you leave you will have a relatively good idea about America (and a portion of Canada). While some very nice places have been left out, you have to make choices."

I have done the Route 87/90 bit several times, and have friends in Kingston, Hudson, Seneca Falls and Batavia, but I tried to balance Niagara Falls with Buffalo, and they lost out (in my mind) to Bridle Veil Falls in Yosemite after traveling through the California wine (and the '49er Gold Rush) country. And some knowledge of Canada is good if only to balance the picture.

I purposely left out the upper Potomac/Shennadoah River area of Harpers Ferry where I live, though it is notable for its wines, very historical, and the spot where Thomas Jefferson called "In my opinion, the most beautiful in the whole world".

JeZeBel will make her own choices, but in my mind the five American cities to make are Boston, San Fransisco, Washington DC, New Orleans and New York, and the three parks areas to see are the Yellowstone/Rocky Mountain region, the Yosemite/Sierra/Death Valley area, and the Grand Canyon/Hoover Dam/Petrified Forest/Meteor Crater areas. In my opinion, the northern California Route 1 above San Fransisco is the most beautiful stretch of highway in the US, followed by the descent into Yosemite, the Pali Highway in Hawaii, and the Skyline Drive in Virginia in the fall. I picked the natural areas as the type of place where you must stop your car, you get out with weak knees, and you wonder what you had done to deserve this.

The three worst cities in my opinion are Gary IN, Reading PA, and Tucumcari NM, with the three most overated natural areas are Put-in-Bay in Lake Erie, Key West Fla, and Nebraska. But hey, make your own list... then duck!