Well several years ago we traveled from Florida to Alaska and back in a 40'er. Stayed in many Provincial Parks in British Columbia and the Yukon. Granted some places were a bit of a challange to get into, but we did it.
Last Summer we traveled up into the Canadian Maritime with a 43'er, New Brunswick, Nova Scotia, Newfoundland/Labrador, and PEI. Some pretty narrow roads up in Newfoundland, but we managed.
You just need to do your own research, granted you will be limited on the number of availble sites in some parks, but most have some larger sites.