I don’t know that a small motor home or a converted bus large or small bus (the small 12-passinger ones) would not go anyplace an auto pulling a trailer could go?
The roads in the USA are very good, I think even a farm or logging road could be traversed by a bus or motor home, or an auto with a trailer.
I don’t see it as an issue that the roads will be a problem in a bug out. Roads may be damaged by earth quakes or blocked by debris or fallen trees or flood water. But these conditions apply evenly to all auto based traffic.
In a flood an old converted school bus may have an advantage because it sits so high. Trailers like the one the original poster is looking at is at a disadvantage in a flood because it’s close to the ground.
_________________________
You can run, but you'll only die tired.