My two cents. Having a sub area for each state may encourage visitors to RVTHEUS to spend more time on the site, and maybe become a member.
A hypothetical example- if I did a google search on RVing in Utah and found a thread on this site, that is great, but that thread would not seamlessly have a collection on all Utah threads in one targeted area. But if all threads for Utah were in one specific area on this site, I may in fact go through more of the Utah threads.
If I am a visitor and see a random Utah thread, maybe I would not be as likely to join and post a question I had, as I would if their was a specific Utah section with dozens of threads on Utah specific RV discussions.
If the forum desires growth in members, targeted categories may be very beneficial in supporting growth. If the forum is not looking to grow, no reason to make specific categories, and not enough posts to make the "juice worth the squeeze".
Build it and they will come.