re: Solo trip - recommendations?

I know you said US but Ireland would be awesome. Rent a car and stay in bed and breakfasts. Spend a day or two in Dublin to check the boxes then head west. Once you get off the beaten path and out of the tourist areas, the locals will talk to you and you can meet some interesting people. Plus, it's beautiful and has plenty of activities. I'm not sure what issues there are with Brexit and covid but Northern Ireland shouldn't be skipped. FYI you can drive across the whole island in just over 3 hours.