Cool comparison, I guess (Also good job at assuming everyone here is American).
I would liken it more to Northern Ireland and Ireland, except with the latter not having any actual ceded land from the former. Or maybe switch those around.
At what point is it considered enough of a division to warrant being “new”? Or is it just entirely cosmetic, where if they don’t look different enough, it doesn’t count? Because we have pandaren, dracthyr, and earthen (soon haranir) on both sides who look entirely identical to their opposite faction counterparts.