We have thought about it, having travelled a lot in the States. There are some superb motor homes to rent, but I do notice that many tow a small car, so that the drivers are more mobile in cities.
Campsites are, I understand, excellent.
But what we do is fly out, hire a car, and start driving. (Having planned where, of course) There are so many cheap and acceptable motels around, just off the interstates and highways, usually next to diners etc. and, if you just have a car, heading into the nearest town is simple. (Exceptions include places like Wyoming and the Dakotas where The distances are immense!)
The only proviso here is that if, for example, you are visiting somewhere like central San Francisco, you might need to book in advance.