arguments for either partrition, or simply moving American forces out of Baghdad and redeployment to Kurdistan, often rest upon two ideas. first, that forcing Iraqis to deal with their own security situation and removing a source of blame -- the Americans haven't stabilized, what can we do? -- might do much. the second idea, and a far more ideological one, is that removing the Western element from Iraq fundamentally undercuts the ongoing narrative in many Muslim minds, that Iraq (and to a lesser extend Afghanistan, and certainly much of the GWOT) is an example of The West vs. Islam. so instead of Shia/Americans vs. Sunnis, it becomes Shia vs. Sunnis, effectively changing the narrative to Islam vs. itself. we might have to accept a more bipolar middle east, with a Syria/Sunnistan on one end, and a greater Iran on the other, with a bit of a Kurdish wilidcard to the north.
perhaps the dismantling of Iraqi borders -- which were always a British fabrication -- might naturally reveal more stable borders drawn up along ethnic/clan lines.