Rockhillmanor: We have found just the opposite. We have no problems with any type of campground west of the Mississippi and many other states in the south. We have no desire to go to the far eastern states so don't know about those.
We easily fit with our 40' motorhome in national parks, state parks, forest service campgrounds, Corp of Engineers, city and county parks - especially in the West. For California we wouldn't fit in state parks but there are plenty of forest campgrounds we have stayed.
You just have to do your research in many ways - there are many good web sites, Google Earth. One thing with having a motorhome, you can detach the toad before entering the park and scout it out first for any obstructions.
There are many of us with big rigs that utilize these types of parks. We see them all the time.