This has me hopping mad! I've been a USAA member for a LOT of years (40+) and always had my TT insured through them. Now they're out of the RV segment and have partnered with Progressive for that. ...
Camper, just like any cargo is covered by auto insurance (with its limits) when house umbrella policy can add to it. I don't buy $50,000 campers, so never worried about it. I would say "consult your insurance agent" but as above shows, you can't trust those guys and I had bad experience with agency in the past as well.