I can get into a discussion, but, basically Bush did nothing to assist peace within Iraq. Quite the contrary. He took an oppressed peoples and tried to oppress even further the most sensitive people within that society.
Al Qaeda was never an aspect to the Shi'ite militias, later known as the Mahdi Army. That terrorist element assisted the Sunnis in their attempts to retake the government.
Why?
Because the Iraqi Shi'ites were already alligned with the Iranian Shi'ites. They never needed the Sunnis. They never needed al Qaeda. A sovereign nation regardless the country is far more powerful than any al Qaeda unit. Oh, they make trouble but they can't destroy an entire sovereign authority.
Yet, alone Iran. Iran is prepared for such issues.
So, the entire assault against the Shi'ites and their cleric is a hideous attempt at creating a continuous war. The USA's military has caused widespread deaths and an escalation in the war. Now, all the sides of the war are armed and financed within their ability to control commerce within Iraq and between it's neighbors.
When Iraq breaks down into smaller provinces/nation states if you will, they will be able to enforce laws far easier than any American military can. The military is there for armed combat, not for police actions.
We don't belong in Iraq.
We never did.
Bush is either a complete idiot, which is possible, or a man intent on killing and oppressing for the sake of a bigger prize, possibly a war with Iran and possibly still the Caspian Sea.
At this point to bring Iraqi National Units out of stable areas of Iraq would be a fool-hearty effort for political leaders in the USA to save face with Neocons. It would reinflame the areas that have security now while risking instead of Baghdad being in turmoil the entire nation will exist in chaos. The stable areas of Iraq, secured by Iraqi National Forces should stay that way.
The chances of an Iraq National Military being formed to secure the most violent areas won't happen without pilots of helicopters and quite possibly small, limited jet capacities. I still believe Iraq needs to be held within the constraints of the allowable defense forces under the Oil for Food Program with such widespread instability in the primary capital, Baghdad. To the extent Iraq is allowed to protect it's borders they should have that capacity, but, never in the hands of people that would simply become another Saddam Hussein. To that end the nation of Iraq is far better maintained as individual provinces equally equipped to protect it's ethnicities that exhibit religious preference.
The central authority can be maintained to support legitimate income and international relations, but, will have to turn away from a Western alliance. Iraq may be grateful for being rid of Saddam but at the same time they are completely disillussioned with democracy and elections that have brought them no stability.
To venure into never, never land; I propose this possibility. Iran can easily supply the Iraqi Central/Unity Government with the same 'type' of military support as the USA if the region sees that as a necessary venue to stability. The USA is not the only military that can support the Iraqi Unity Government. In putting Iran's military in place of the USA military there would be more incentive for Shi'ite militias of Baghdad to join a unified force with training that is more agreeable to that infantry. At least Iran and Iraq would have a matched set of soldier and the chance of any instability would be eliminated. I am confident under that leadership the Sunnis would be threatened and set up the violence within the country. But, it would eliminate the sectarian violence and the confrontation would simply be to bring the Sunni insurgency and al Qaeda under control. The risk, of course, is a wide spread attack on the Sunnis.
That is a misnomer to think an Iranian guided military would be reliable in their mission, but, to realize Iraq is 60% Shi'ite and the north completely Kurd, the idea has some merit. The Kurds could be supported by a smaller USA military detachment to protect them in any transition and that is where PIVOTAL balance comes into play. The USA would be in the region under a stable Kurdish democracy while Iran stabilized the Shi'ite military deployement and expanded it through recruitment of militias into the Unity Authority.
In simple terms. The Iranians would hopefully carry a greater influence in the military organization of Iraq while the USA stood by in Kurdistan to protect any advancement by any military into the area. It would then be upto the Sunnis to lay down their arms and accept the Unity Authority of Iraq. If such a plan is not tried and should it fail then Iraq won't exist anymore and there will be three sovereign authorities, leaving Al Albar to the Sunnis. The USA would have a presence in Kurdistan for as long as needed and perhaps what would return would be no fly zones.
None of this is ideal, but, do pose workable solutions leading to stability and not an escalation of war.