Do you have to have a RV licens to drive a RV?

Answer 1

If you are driving for non-commercial you do not need a special drivers license in the US.

But if you are driving a motorhome with air breaks commercially you will need a CDL with the Air Breaks endorsement.

Answer 2

Laws on this will vary according to state of residence. Some states do not have any additional licensing requirements for RVs, while others may require a chauffeur's license, or a non-commercial Class A or B. However, that's only enforceable within that state, as there is no federal standard insofar as licensing for an RV goes, except to say that they're exempt from requiring a CDL when operated as a recreational vehicle not on a for-hire basis.
Air brakes have absolutely nothing to do with whether or not a vehicle requires a CDL, and there is no such thing as an air brake endorsement on a US license - if a commercial driver does not complete and pass the written air brakes test and conduct their road test in a vehicle equipped with them, then they get a restriction prohibiting them from operating a Commercial Motor Vehicle which is equipped with air brakes.
The only time a CDL is required for a recreational vehicle is when it's being operated on a for-hire basis (e.g., transported from manufacturer to dealer or a driver hired to drive it for any other reason), and it is either:

A: A single vehicle with a Gross Vehicle Weight Rating of more than 26,000 lbs., or is a combination with a power unit which has a Gross Vehicle Weight Rating of more than 26,000 lbs, but in which the trailer does not have a Gross Vehicle Weight Rating of more than 10,000 lbs. In this instance, a Class B CDL would be required.
B: A combination truck and trailer in which the combination has a Gross Combined Weight Rating in excess of 26,000 lbs., and the trailer itself has a Gross Vehicle Weight Rating of more than 10,000 lbs. In this instance, a Class A CDL would be required.