Agreed, Iraq is an artificial creation.
I would hope that some sort of loose federation is possible, but break-up is a possibility. The Shias hane more in common with Iran, but the Bagdad and Kurdish business men don't like the strong Muslim religious bosses there. The Kurds are semi-independent now, but their militants could cause trouble with Turkey. The devolvement into provincial management promoted in the paper I linked recognizes the inevitable.

Who will buy the security? An interesting question. The U. S. government has been paying private concerns for part of it. A portion of the billions being generated for Iraq could be used for payment (Just what is happening to the money now?- hard to find a clear answer).
Would a change to Democratic control in Washington mean that U. S. troops will leave within a year or two? I doubt it.

All bets are off if Israel and/or the U. S. attack Iran.