Why do you believe the split will be into two countries? There is a whole conservative heartland stretching from Oklahoma up through the Dakotas, over to Idaho, and then down into Wyoming and Utah that has nothing in common with the eastern part of the country or Dixie, and certainly nothing in common with the left coast. If this country is fated to split up then I'd willingly hitch my wagon to that country and let the rest of you stew in your own juices.
I meant that the old line between north and south would play a big part in how the new nations (I could see as many as 5) would be divided.
I actually agree with your comments about the Midwest. The way I would see things splitting up is:
Northeast (basically the old union)
South (basically the old confederacy)
West - all the pacific coast states
Mountain - all the mid west states you stated
and Texas standing alone.
that's how I see a 5 state solution.
Although it would be hard for the Midwest to be land locked, and I see Texas as the natural pairing for them to gain port access, which would bring it down to 4.
Then Texas would act as the gateway to the South and I could see a new nation eventually emerging which included the old south, Texas and nearly all the west and midwest states except those that border the pacific.
Arizona and New Mexico would be wildcards, which could do anything including merging with Mexico.