I can't really imagine any state not having at least one campground. I mean, camping is so prevalent that it would be odd not to have it.
Personally, I think when choosing places to go is to find campgrounds close to the attractions that you wish to visit. For example when we went to California, I wanted to see the Ghirardelli Chocolate Company, the Golden Gate Bridge and the Winchester Mansion. So we tried to find accomodations that were central enough.
Also, I think in Florida, it would be really easy to find campgrounds due to the numbers of snowbirds, plus, Disneyland is there and that caters to families.
Now with the internet, it is so easy to find ideas. We used to have to depend on maps and tourists guides coupled with city guides and brochures from information booths so I think the selection would be numerous with the internet research.
My website has lots of information on campgrounds in California... I can't help with the other States, but check with reserveamerica.com They do reservations all over the place
my webpage is www.boa-magazine.com
How that helps