I have not yet encountered a restriction in the 21-23 foot range, but I've also not taken a RV to New England. Through most of the parts of the country where I've been, the Deep South and mid-continent from Appalachians to Sierras, I haven't seen RV site length or access restrctions until 30 feet or longer, and even those are rare.
There are, however, in many public parks, camping areas where the parking spot for a site is sized for a standard vehicle (less than 24 feet) and that is because the site is for setting up a tent. Small RVs, like Pop-ups and camper vans, can sometimes use these, but not larger vehicles, and these small sites typically do not have RV hookups.