Most of what you mention could happen after the US election, but Bush will not let things 'fail' before then. Until the election, Bush will dump whatever forces are needed into Iraq to provide a semblance of stability.

In fact the most likely course to end up with Iraq divided is if Kerry wins and caves to the radical lefts demands for immediate pull out. If that happens the UN will flee also and the country will either collapse in short order or a new dictator will seize power.

If Bush does win the next election, I expect to see a semblance of a country. But it is liable to be chaotic and violent and the US largly confined to military zones. However, Bush could wash his hands of Iraq if he wins the next election and decides that North Korea is the next target.

Jay