Do most state parks have a 30-foot length limit?

Even for Ca, I'd call first. Many state parks have a posted limit due to being on the coast or in the Sierras. But they're based on old roads in many cases. One state beach had a 20ft limit because of the road getting in. They've redone the road and can easily fit a 35ft. The limit is still there, but rangers know the reality and will tell you.

Same in the Sierras. My favorite campground has a 30ft limit. But a 40ft pusher easily fits with room to spare since they redone access road.