[JRTJH]

That wall is not a "weight bearing wall" in the sense that it supports the roof, but I'd wonder if it is a "structural rigidity wall" in that it provides rigidity to prevent the trailer sidewalls from flexing laterally along the trailer frame rails. You may be OK with the removal, but you may also find that there is excess movement at the sidewall/roof seams and along the floor/sidewall joints.

I'd recommend watching closely, you may soon find leaks along the aluminum molding that covers the TPO roof and the sidewall.