Perhaps in USA is very much unevenly distributed? I visted a couple of big cities in California and the situation is abysmal, I don't know of any place in Europe even close to that, still have to see campings in the middle of a big city. I could't see the same in other cities I visited, e.g. Las Vegas and Miami.
The numbers seem to say it's the same in theory, in practice my experience is that it very much doesn't _feel_ the same.