I had a tv mount from the factory on the outside of our last trailer, but I don't know how they did it. We never used it. I would assume they put the mounting screws into one of the structural members, not just into the siding, unless there was a backer that was installed in that location.
As Seilerbird said, please be considerate to your neighbors when using an outside tv. Not everyone is interested in seeing/hearing the game or show that you are watching, and some may take offense to some of the shows on tv.
We have used the outside tv we have now at our house for our granddaughter and a few of her friends to watch a couple of movies one night. That tv is mounted in a compartment though.