Depends where you go. Last year we took the blue highways from Blaine WA to Arches NP in Utah, crowded, further south was Monument Park, lots of room. We stopped in places like Wells NV, no prob getting a site, can't remember the name but along the blue highway in NE NV, sign said golf course RV camp, mile and a half later, a beautiful RV park only half full. Stay off the beaten path, we usually don't make reservations, we always find something, never WalMart.
Goldfield NV is a run down old mining town, many RV parks, few in them, we camped in one that had four spaces, us and one other. We don't like crowds or neighbors, and don't seem to have problems finding that.