Like the others, I don't understand why you're dealing with USAA instead of Erie. But since you are, here's my advice.
I dealt with USAA before, when someone who had their insurance hit me. They told me not to bother with getting my own estimates, because they would send their own adjustor. I laughed and got estimates anyway, which turned out to be a good thing, because that's how I realized how badly their adjustor was lowballing me. In my case, the car was a POS but was cosmetically perfect before being hit. The wreck was minor, but it tore off a chunk of the black rubber part of the bumper (this was in the 80s - I don't know if anyone even has those type of bumpers any more). Their adjustor, rather than specifying that this needed to be fixed, had simply allocated $50 for me to "put up with it." I politely told him that was not going to happen, that the car was cosmetically perfect and that I expected it to be put back in that condition (truth was that I had no intention of fixing it, but that doesn't mean they didn't owe me what it would have cost had I chosen to do so). The adjustor was an hour away, and he said that rather than drive to my town *again*, he'd give me what I wanted. Score one for me.
Many years later, I dealt with my own insurer twice over totaled cars (I wasn't at fault for either). Both times they offered about 25% less than what the car was worth according to locally obtained comps. Both times we refused their first offer and insisted on the actual value (plus tag), and both times we got it. The first time, it took a lot more arguing, and a threat to take it to court. The second time they looked at our comps and quickly agreed to a reasonable amount. But we never accepted a check from them for the first offers - we didn't sign anything until we had what we wanted.
In your case, I would present your comps, and tell them "Look, this isn't coming out of your pocket anyway, since Erie is going to have to pony it up, so just pay me what it would cost to replace my car and be done with it."