That was sort of how I did it many years ago.
I had a KOA guide that told me where the camp grounds were, and if I did not see a good spot before that, I used them.
Back then, they always seemed to have space for a tent, even on 4th of July in Wisconsin Dells!
I often found nice places to camp before needing the KOA, some fantastic places for cheap or free.
I had to sleep on the beach in California (Newport beach at Balboa pier?).
Not many campgrounds in LA!
Highlights were the KOA at Devils Tower, cowboys had a corral to practice roping animals and so on.
Camping in a state? park between Cody Wyoming and Yellowstone park, along the Yellowstone river was quite stunning. And cheap.
In the days of cell phones and gps, it does not seem like much of an adventure...