Our Champion 3100 inverter generator easily runs our rig's AC tested at over 8500' elevation, still has power left to run our Iota converter and a couple of fans too. Not sure which model you have but many report running their AC unit successfully with the Champion 3500 watt open cage non-inverter version.
Gasoline engines lose 3 percent of their rated power every 1K' elevation, since we most often camp between 7K' and 9K' we lose a quarter of our Champion 3100's rated power, not an issue thus far as a simple press of the remote and she readily purrs into life. They now have a 3400 inverter genny for added oomph.