To split Iraq up would be to bow to the wishes of the jihadists and admit the fact that Iraqis are not civilized enough to live in a multicultural society
I'm not sure the British are civilised enough to live in a multicultural society, never mind the Iraqis. (Usually at this point my wife would remind me, lets see, how does it go, "We Persians were living in cities when your ancestors were still painting their arses blue", yes, thank you dear.)

Tribesmans points are excellent, for my part I feel the intractable issue of Kurdistan is enough to scupper the idea. The Turks (NATO member, EU supplicant and with a genuiely effective military) will never accept andindependent Kurdish state on their borders, what with all the naughty ideas it will give the Kurds within Turkey.

Besides which I am not too sure how serious the issue of interethnic tension in Iraq is, as opposed to the presence of US troops acting as a magnet for Wahaddi madmen from all around the region. The Sunnis have been on the pigs back for years, now they are going to be a minority, deal with it. Admittedly it IS rather stupid to go into a country and proclaim democracy without asking yourself who the newly enfranchised voters will support, but "rather stupid" and "American foreign policy" have gone together for years. (Phillipines, South America, Vietnam, Israel, etc etc) (This is not an anti-american remark. I wish the USA did have a sensible foreign policy, it would make the world a better place.)

IMHO the only option now is for the US to resign itself to "peacekeeping" in Iraq for the long haul. You broke it, you own it, that's the rule. That also means preventing the shias joining Iran and I couldn't care less if that is antidemocratic. IIRC the British undertook a similar sort of exercise in Egypt in 1882, announcing we were only there for a short while to support the native leaders and would leave as soon as possible.

40 years later we gave them partial independence and we only really left after WWII. These are the sorts of timescales Amercia needs to think of for real nation building. This empire-lite crap she is up to now is dangerous.