For me, it is the voltage drop, not the amperage of the circuit. Power cord size, wire guage to the outlet, condition of your breakers in the trailer itself, condition of the plug itself, all connections tight, and of course the starting needs of the AC that come into play here.
Best thing to do is check all of the above and then use a volt meter to assure yourself that you are getting at least 108 volts.
I find that even when I am getting minimal voltage that on a 20A circuit my plug will be warm or even hot. If I am able to feel the wiring of the circuit itself from the breaker, it will be quite warm. Resistance in the circuit equates to heat which steals voltage............Dennis
Dennis & Susan
D&D Farms, Sugar Valley, Ga
Registered Boer goats