What Percentage of RV Parks are Cat Friendly?

If they are indoor cats there is no issue at any park. If you plan on letting them out to roam you'll have a problem pretty much everywhere.

Last year we spent 8 months on the road, mostly in the southwest, and talked to a number of people with pets. A number of the cat people said they had lost cats who went out by themselves, probably to predators. Coyotes are everywhere now, as well as whatever local predators are in the area where you are. Just saying, be careful.

I cant imagine why there would be a problem. Just go by the rules, keep it on a leash, clean up after it, keep it on your patch of ground, no constant barking. :)
Hit the easy button.

We have traveled with our cat for 5 years now, it stays inside. I have never had any complaints of difficulties at any park.

I have never been to an RV park that even cared whether you have a cat or not. Usually two pet limit. It's anti cat people you need to worry about. Only problem I ever had with cats was them urinating on my wheel covers and using my landscaping as a litter box when left to roam freely. Leash trained? It's more about responsible pet ownership. You have nothing to worry about unless your not the later and parked next to me. Just kidding, lol You'll be fine.