That's certainly part of it. And part of the reason that Republicans control more states is (as TFA makes clear) that they made a particular effort to win them

That's certainly part of it. And part of the reason that Republicans control more states is (as TFA makes clear) that they made a particular effort to win them in order to control the mapmaking process for Congress. I don't know which party is more likely to gerrymander (or gerrymander more shamelessly) if given the chance, though it should be calculable in principle.