Our Cardinal is listed at 25', but overall length is more like 27-28'. We did a trip west a couple of years ago and had little to no problem at state parks, Nat'l forest, and Nat'l parks. The one place we experienced a problem was at Yellowstone. No problem at Grand Teton, but tried to get into YNP and because we hadn't reserved a site and everything was taken for RV's our length. We drove through one of the campgrounds and it looked like about 85% of the sites were too small for us.
We like our current size, but most of that is due to the fact we have twin slides (one on each side of the main body). This gives us plenty of room in that area, but not one in the bedroom. We've been looking for a nice used 29-31 footer, but they seem hard to find, but we are a bit picky. Since our TV is only a 3/4 ton we don't want to get much larger.
Here in Michigan (state parks) very few if any problems with length. Florida state parks are sometimes a bit smaller on average, but we've almost always been able to get a site where we wanted to....other than the Keys that is.