We went from an 18 foot travel trailer, to a 31 foot, to a 35 foot, and am still camping at the same State Parks we tent camped in. The only difference is, we have to select our sites by length when we make reservations.
In private parks, we've NEVER had a problem getting a spot, at any KOA, any GoodSam, or any Mom-and-pop campground, anywhere.
Check the reservation sites for the state park you are considering. The length of the sites should be indicated. When selecting a site, use the true length of your camper, bumper to hitch, or bumper to bumper. Now, you may not get that spot that's covered with a 100 percent canopy of trees right along the water's edge, but that's the trade off for a larger RV. But, we've never been to a campground anywhere that had too short of sites. We've been turned away because there was no room and no reservations possible, but not because of trailer size.
Wisconsin has some really nice campsites, but sometimes navigating through the park can be an interesting experience though. And we were at a couple State Parks in South Carolina that had really nice campsites, but navigating the turns to get there was ... well ... "interesting"! But I chocked that up to experience, and it gave me an opportunity to increase my towing skills! :E Which it did!