In traveling mode, 30 foot C motorhome with no toad, I use advertisements and directory listings to identify RV parks in cities with access to public transportation.
Outside urban areas, and certainly in any place that could be a campground rather than a RV park, I look for shuttle offerings, but usually I just use the motorhome to get around. Not much more than 15 minutes to break camp or set up again, if you don't make the procedure elaborate, and in rural areas getting around in a motorhome this size is not a problem. Experience has been between Appalachians and Sierra Nevada; vehicle size might be more of a problem in the densely populated coastal areas, but once population reaches a certain density, I expect to find public transportation.
Tom Test
Itasca Spirit 29B