I am not an attorney, I believe Down the avenue is, so hopefully he/she will chime back in.
But you might consider the following.
1) I would not take the adjusters word on the frame as gospel, if you are concerned, pay on your own if you have to , get it checked.
2) I believe as you are not the at fault party, you can have the trailer repaired at a facility of your choice.
3) Camping World, may well hold a contract with USAA, in which case they will repair the trailer cheaper, but the will use after market parts, not OEM parts. and the will not search for hidden damage. As they are trying to meet a price point to get the business. I believe you have the right to demand OEM parts, as you are not the at fault party. I would if it were me, for sure get another estimate or two.
4) Loss of use, this is something the insurance is not going to tell you about. You may well have that coverage, so under the policy terms, you are owed compensation for the down time.
5) As you are probably figuring out, you are playing in their ballpark, and you like me, do not know the rules. Which is why I strongly suggest you hire an attorney.
6) I agree, it is a giant hassle, but end of the day only person looking out for you, is you and your attorney. If you end up with a poorly repaired trailer, that 2 years from now is falling apart, I guarantee, the insurance company response is going to be, (sorry to hear that, but unfortunately, nothing we can do, followed by a click)