I would start by removing the 7 pin connector from the trailer umbilical cord.
There are a couple of things that might have happened.
1.If you connected the charge line from the TV to the ground/common connection in the Ucord (umbilical). I would have thought a fuse would have blown in the TV.
2.If you connected the ground/common of the TV to the charge line of the trailer it would also have caused a short. But there should have been fuses in the trailer to protect the wire.
Again remove the 7 pin connector. Separate each of the wires so they are not touching each other or the metal on the trailer. Also disconnect the battery in the trailer and unplug the shore power or at least turn off the converter.
If you know how to use a VOM meter: Put the meter on the Ohms scale and read each wire to ground/common. Only one (the ground/common) should show a short to ground. You will get what looks like a short on any circuit with light bulbs, it may or may not read absolutely zero in those cases.
If you don't know how to use a VOM and want to learn get back to us.
You can also use a battery charger and check each circuit. Most modern battery chargers have "crowbar" protection and will shut off the output if there is a short. Connect the black lead of the charger to a clean spot on the frame, then connect the red lead to one wire at a time on the Ucord and walk around the trailer and see what works. The white wire in the Ucord is the trailer ground/common in most cases, if you touch it with the red charger lead, the charger will probably shut down. Make notes of what happens with each color of wire. On circuits like the tail/marker lights where there is a significant load, you may see a spark when connecting the charger. This would be considered normal.
In a trailer of this vintage the wire color code is different than todays trailers. Make notes and let us know what happens.