Iraq stands at the junction of three different and competing cultures for the control of the country. Kurds, Shia and Sunni Arabs all want to control their own affairs and that of the Iraqi state. Since each of them have their own distinct identity and their own supporters the potential for conflict is great.
The first group entails the Kurdish people who have developed an independent living arrangement for their 25 million people spread among Turkey, Iran and Iraq. Despite not having their own state they do have their own government, schools and military. They are in effect a state without borders and without international legitimacy. Their race for statehood started in 1920 during World War I when President Woodrow Wilson promised them independence in return for support. The Treaty of Sevres was to have accomplished this. However, when the Ottoman Empire was reformed into Turkey the Kurdish people lost their legitimacy.
Sunni Arabs make up the second group of contenders for Iraq. Even though they are slightly outnumbered by the Shia in Iraq they are major contenders for the country because 95% of the 1.3 billion Muslims worldwide are Sunni. They are the orthodox Muslims with a level of legitimacy unseen by the other groups. In recent times there has been a surge of calls for the reforming of an Islamic state and leader (Caliph). Therefore the Sunni insurgents are supported by other Muslims with weapons, money and recruits. Throughout Chechnya (Caucasian), Afghanistan (Indian), and Iraq (Arab) you are beginning to find coordination of tactics and recruits. It is becoming common to see Muslims from different nationalities fighting along side of each other because they have the same vision for Islamic independence.
The final group is the Shia which represents approximately 3% of all Muslims worldwide. The Shia became famed with the Iranian revolution which is one of the first Shia Muslim states. Iran is actively supporting the Shia in Iraq and trying to export their revolutionary ideas throughout the region. As we can tell from the past rhetoric between the U.S. and Iran that they are not supports of American democracy and make every attempt to thwart it. Due to sanctions and rigorous development Iran has developed their own military industry that is sophisticated. If these weapons show up in Iraq there is likely to be great bloodshed.
Iraq is a country on the verge of civil war. The three contending groups each have their own particular strength. The Kurds have a pre-established governmental institutions and military, the Sunnis have the support of the wider Muslim people and the Shia has the staunchly anti-American Iran. If the U.S. looses control of Iraq or withdraws from it in the near future it is unlikely that the country will be able to withstand a civil war where each group has a highly concentrated region. The end of civil war could potentially mean three distinct countries all competing for Iraq's oil reserves. It is also likely that such a war will not be easily quenched and may produce one of the world's worst humanitarian crises. Once started it is wholly possible that Sunni countries will begin to get involved against their Iranian rivals. All of them will be against any Western influence and are unlikely to heed any calls of quiet until they have exhausted their resources.