Many brands of trailers have a piece of thin steel sheet metal just under the wallboard. Use a strong magnet to find and outline that piece of steel and then mount the TV using sheet metal screws that only penetrate the wall by about 1/2".
If there is no piece of sheet metal to be found, then you would need to use a stud finder and use screws that are less than wall thickness.
Before you do anything, we should know if you have laminated sidewalls with aluminum framing, or "stick & tin" walls with wood studs and aluminum siding.