Philly has a few spots of interest, on the whole, I don't care to visit again. I find DC quite interesting, and much of the city is "nice", a lot of parks and green spaces. I was there two years ago with my daughter during the cherry tree thing which was interesting. We walked a lot.
I've been to Minneapolis, Minnesota once during July, it seemed fine, that was 1984ish.
I was trying to think of the largest city in the US I've never visited. It might be something like Augusta, Maine. Some I just drove through, like Green Bay.
We drove my Turkish friend to the airport two days back and the traffic coming back was horrible, on a Sunday. Something was amiss, I tried to go around and it was horrible too.