You almost certainly don't want to do that. You'd need a transformer that can handle over five kilowatts, and will probably be too big to hide on your RV (I've seen similar ones for over a thousand dollars, almost two hundred pounds, and that are a 20" cube.)
But, if you change your generator from a 110VAC to a 220VAC, you'll have to figure out another way to power your local 120VAC appliances. Maybe you'll need a 220VAC to 110VAC transformer, but the power requirements for that would be far lower than for what you're asking.
If these min-splits are meant for RV use in the US, then the manufacturer will have dealt with exactly this problem again and again and again. Call them and find out what they suggest.