Americans have changed their habits since most of the tent campgrounds were constructed especially after WWII. National Parks in particular have been slow to accommodate RVs. Forest Service campgrounds have done a little better.
I like having a smaller RV because it fits everywhere, say under 22 feet. You can commute to parks from private RV parks outside, but it is a different experience. I am usually happy to give up some amenities at a dry site in exchange for quiet, scenery and wildlife sightings.
Yellowstone is an example of a park that is LTD, loved to death. Go in May or Sept and forget the summer.
