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. ...
Ask the folks on the homeowners policy about adding some coverage, no matter how small specifically for the trailer since it may be damaged in a catastrophic even such as a flood or storm. Having your amount of personal property coverage raised will give you a much stronger position IF there were ever a claim against the homeowners policy.