Brice Canyon is wonderful. Not overly crowded.
Just get in a car in southern Utah, and drive a little. Stunning national parks are everywhere.
I have done Acadia in Maine, and the great Smokies are wonderful.
One of my favorite photos of my car in the Smoky Mountains area.
I would say my wife and I loved arches national park the most. After a most of a day there, we headed to Mexican Hat, Utah. It is a beautiful road, the comes to cliff, and a very slow winding very tight
cars only, no trucks, motorhomes, or cars with trailers allowed decent to the valley floor. And a short drive to Mexican hat. We had motel reservations ahead of time, as there is just one motel there, next to a river. We filled up at one of the just two gas stations in town. The next day drive through the most spectacular parts of the USA, Monument Valley.
Also in northern Utah is dinosaur national park. If you are into dinosaurs, it is really cool, but rather crowded.