While unlikely the events of the game timeline would occur, it's not impossible as CDAT has detailed. It's a case of a series of bad choices and enemy action coupled with fate and luck colluding to screw things up more than usual.
Now, back to the OP. I don't know enough about the US succession requirements to accurately comment, however I do see the SoD either being used as a figurehead to bolster one sides legitimacy over the other, or even a third side forming around them.
The potential for chaos is breathtaking!
