I think a lot of it is going to depend on location and density. I'm in California and have only traveled in the West in my RV. There are plenty of gas stations that I can't get into, but there plenty more that I can easily get into. I've never had a problem finding one. But one thing I wouldn't do it drive through Los Angeles, or San Diego, or the SF Bay Area without having enough fuel on board to get through. I don't want to be trying to get off I-5 in downtown LA trying to find a station big enough to get into. But when you carry 100 gallons and have over a 700 mile range it's not hard at all to avoid having to fill up in the cities.
One thing to check for is overhead clearance. Most newer gas stations, especially ones that carry diesel, have plenty of overhead room. But older stations may not have so much. I did turn into a station once and got right up to the overhang and thought it didn't look like enough room. So I stopped and got out and looked, and sure enough I wasn't going to fit. I was towing my truck and it was still out in the street so I did end up blocking traffic a little while I unhooked the toad and got backed out of there.