USAA underwriting does vary from state to state depending on state insurance commission/regulations.
But, I have noticed USAA is moving a lot their direct non-automotive (motorcycles/ATV/etc) underwriting to Progressive. Perhaps I purchased my rider prior to a change in USAA underwriting policy for recreational toys. If such is the case, those policies are grandfathered and one may want to think long and hard before moving to a different insurer.
After reading the fine print, I prefer Farmers toy policy to Progressive. Unfortunately, Farmers is not licensed by the NC Insurance Commission so I'm stuck with Progressive through USAA for my motorcycles. Until we relocate to NM...some day.