You can run a single air conditioner on 20A or perhaps even a 15A circuit
A single air conditioner typically has a 20A circuit breaker but only uses 13A of current.
Provided that you turn off most of the other electrical load in your RV, you will be able to run a single air conditioner on a 20A and perhaps even a 15A circuit.
Other loads to turn off while running the air conditioner
You will not be able to use other large loads concurrently with the air conditioner - such as microwave range
A air conditioner does take need 15A for a second or so while starting, so depending on how fast a 15A circuit breaker reacts you may or may not be able to run the A/C on a 15A circuit breaker.
We hope to run the air conditioner on a 2000 watt AC
generator by reducing the startup current