I think what aceinspp is trying to say, is IF you have a smartphone, and internet access and you are capable of searching for a state or Fed run campground you should have no trouble finding one. The only exception to this is camping south of northern FL in the winter, or north of Ohio in the summer, where even commercial campgrounds fill up.
I have never stayed in a commercial campground because of the cost difference between gov't run campgrounds and for profit... just have to plan anywhere from 11 months for state-run southern campgrounds (or MI or WI campgrounds in the summer) and 6 months for FED run campgrounds. That is the furthest out that you can reserve. Reserveamerica.com has that information
Even out west in the summer, the big parks get filled, but you can almost always find a no-services Fed Forest Service campground site on the day that you arrive, if you are not arriving too awful late. I have had to camp alongside a deserted state route road more than once in Utah one summer, before I learned this lesson.
Now if you want swimming pools and dog walk areas, certainly I would look to the membership places for those amenities.
Certainly have fun on this planned trip!
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