Twenty states...maybe. The ones that are already owned by Rats.
There's a whole host of terrifying crap that they will be able to do without effective pushback from the red states.
This, however, isn't one of them.
I believe your right, 20 states max would sign on to this (need 75% of the states, or 38 as of now).
There are 15 states right now that have rat "trifectas" (governor, state house and senate) so those would presumably be the automatics. Toss in another 5 "mixed" state governments to get to the 20. I think it's safe to say...for now, that getting to the 38 is impossible. If they do manage to add 4 new (D) states in the next 2 years, they would need 41 out of 54. Still not happening.
So we appear to be safe from this power grab. Now, of course, this presumes that they will follow the Electoral College rules to begin with.