House AC went out can I hook up to 20 amp gfci

One of the nice things about an RV is that if something like the heat or AC goes out in your house, you can use the RV. As others said, just run one AC and nothing else and you should be fine. Usually worst case, you trip a breaker. I had a previous Class A that didn't mind a 15A for AC. My current FW prefers a 20A - it will trip a 15A even with only one AC running.