My Travel Trailer is 35.5 feet long (real length), and my truck is 22 feet long. (57.5 feet), add 2.5 more feet for my cargo carrier on the back of my trailer bumper and that makes my length 60 feet (just legal in Indiana!).
No problem with campsites and parking both. BUT! it does take some searching and checking going to a new location. State Parks will often give the length of the campsite pad and a description. We always compare with Google Earth satellite imaging to see about actual trees and such.
Bottom line, with prior planning, there is no problem with most parks, private and state or federal owned. Just do your research before making reservations.