The smaller your rig, the better your chance it will fit everywhere.
The US Govt has been building campgrounds since the 1930s. The big years for construction were post WW II and the CCC days. People tent camped in those days. RVs have become much more popular in the last 25 years. Many campgrounds need to be updated but it takes a lot of money that the Govt claims they do not have. People resist rising entrance fees and camping fees.