Nate Cohn draws the map of these 61 United States:
What would happen if all of them succeeded? Each new state would get two senators and its share of electoral college votes. We ran the numbers and recalculated the 2012 presidential race.
In this bizarro United States, the GOP would have a structural advantage in the expanded Senate, and Barack Obama would have had a tighter fight against Mitt Romney in the electoral college (which he won, in reality, 332–206).
Of course, Cohn assumes that once the states seceded from their parent states—unlikely, in cases where the new states would reverse the existing state's party affiliation—the other states would let them in.
It's an interesting statistics issue, but alas, we're stuck with Texas and the rest of the former slave states that want to re-litigate Article IV.