In the 20th century, the Muslim world created a vision of religious nationalism. Turkey, for example, had to be ethnically Turkish. Kurds, Armenians, other minorities didn't have a place in such a vision of a nation-state.
The U.S. cannot force Sunnis, Shias, and Kurds to make peace or to act for the common good. They have been in conflict for 1,400 years.
The Kurds were the only people in Iraq who were completely unguarded in expressing their gratitude to the United States for setting them free.
If they make the deadline because the Shiites and Kurds essentially rammed a draft through over Sunni Arab objections, there will be hell to pay.
Iraqi national identity under Saddam Hussein never truly incorporated Shiites or Kurds. Sunnis, who identified most closely with the Iraqi nation, remain in some ways disenfranchised relative to the other groups, or at least they perceive themselves that way.
Whenever a Kurd wants to measure the depth of some foreign leader's commitment to Kurdish autonomy, he listens for one particular word. That word is 'federal.' Anyone who will say he favors Kurdish federalism can be counted a friend of the Kurds.
Under the Assads, Kurds were forbidden from learning their own language at school, or even from speaking it in the military. The result is a generation of Syrian Kurds, many now in late middle age, who can't write their own language.
By very conservative estimates, Turkish repression of Kurds in the 1990s falls in the category of Kosovo. It peaked in the early 1990s; one index is the flight of more than a million Kurds from the countryside to the unofficial Kurdish capital, Diyarbakir, from 1990 to 1994, as the Turkish army was devastating the countryside.
So the idea that you could put Kurds, Shiite Arabs, and Sunni Arabs in a nice, liberal, federal system in Iraq in a short amount of time, six months or a year, boggles the mind.
There is absolutely no doubt in my mind that Saddam Hussein had and used significant weapons of mass destruction on his own people, both the Kurds and the Iranians.