The only wars in the history of the United States that have lasted as long as the war in Iraq are the Vietnam War and the "Indian Wars" for a century, a catch all that military demographers use to sum up a great many conflicts in a century of North American counter-insurgency actions. There is no clear end in sight, many see the conflict continuing for at least another five years if it is allowed to endure by American politicians. Nobody thinks that the war is in an end game, although the U.S. presence may wrap up if a Democrat is elected President, which seems likely.
One West Point scholar called the current conflict a mosiac war, really a collection of regional civil wars and counterinsurgencies only dimly related to each other.
This characterization comes through in the provincial level casualty numbers. No Americans have died in Iraqi provinces entirely within Iraqi Kurdistan. American casualties in the Southeast Iraq region striving to unite under a region Sumer government, most of which is Shi'ite Iraqi have been low, and remain low even when other coalition partner casualties are taken into account (which isn't to say that the region has been in a state of peace).
There have been moderate casualties in the provinces North of Baghdad which are partially in Iraqi Kurdistan, and partially in Sunni Arab strongholds.
More than half of American deaths have been in Sunni Arab dominated Anbar province between Baghdad and Syria, and in Baghdad itself. Increasing religious segregation in Baghdad, a Shi'ite militia truce, and a U.S. troop surge concentrating on the capitol city have reduced deaths in Iraq, but attacks have renewed in vigor along the contested Sunni Arab-Kurd divide in the North.
Half of the suicide bombings in modern history have taken place in the Iraq war, about 900 out of 1800. These attacks have caused a disproportionate share of the deaths in Iraq, killing about a dozen people each on average. About 90% of those have been carried out by foreign fighters, with Saudi Arabia providing the leading source of foreign fighters. Most foreign fighters in Iraq are 18-30, with an average age of 22, and they tend to be Sunnis. Very few are college graduates. Most finished high school or are high school dropouts (which carries less of a stigma in most of the world than it does in the United States). Foreign fighers tend to be poor or middle class, come from big families (often six to eight children), and are looking to make a name for themselves. Mostly, they were either unemployed or stuck in menial jobs at home.
While their families and religion look different, demographically, they have a lot in common with American enlisted soldiers, especially now as the Army has let its standards for recruits drop.
We are also on the brink of the effective dates and timelines of a great deal of Iraqi legislation designed to facilitate the decentralization of the government to a point that approaches soft partition. If the vision currently on the books comes into being between now and the summer as scheduled, a regional government will be in place in Sumer, a new round of elections will shift clout to state governments outside Sumer and Kurdistan, and the uncertainty that pits Kurds against Sunni Arab transplants in Kirkut will be resolved -- probably in favor of the Kurds. A new oil law could likewise decentralize oil revenues, giving regional governments greater autonomy.
In addition to homogenity, the state and regional governments would not face the supermajority requirements imposed by the current Iraqi constitution at the national level (in order to prevent eithe Kurds or Shi'ites from shutting each other out), which has made the nation ungovernable by civilian authorities, prevented civilian reconstruction from moving forward and hampered efforts to establish a viable domestic security force.
Baghdad is a shambles. It still isn't safe. Even the Green Zone sees regular scambles to avoid mortar shells or bombs. There are essentially no ethnically mixed neighborhoods left in the city, and the Sunni Arab neighborhoods have become walled ghettos like mini-West Berlins within a hostile city.
Most of the nation's professional/managerial middle class, which allowed pre-war Iraq to be one of the few Middle Eastern countries with a viable non-oil economy, has fled abroad, mostly to Jordan and Syria. The tiny Christian minority has likewise fled. Iraqi Shi'ites and Sunni Arabs who were minorities locally, have likewise fled to friendlier domiciles within Iraq abandoning their homes and businesses.
Of course, it has been repeatedly confirmed that there were no weapons of mass destruction in Iraq, that there was no link between the Iraqi government or its leaders and terrorist threats to the United States, that the invasion would not be cheap and self-financing, and that we had enough information in hand to know all of those things in 2003 when we started the war. The administration lied to start this war, and failed to engage in even minimal planning to cover post-invasion operations -- a State Department plan to do that sat on a shelf until it was hopelessly out of date, overcome by years of neglect and changing conditions.
We are in Iraq as a result of the "you broke it, you bought it" Pottery Barn rule until we can come up with a way to leave the nation in good order with a shred of dignity. We have little or no local influence, have discredited the idea of democracy, have destroyed U.S. credibility on human rights, and have committed to spending something on the order of ten trillion dollars in this mess, while giving up about 4,000 American lives and wounding 30,000 Americans so far -- far more U.S. soldiers have come back with real but more subtle internal traumas as a result of the war. There are about 1.5 million Iraq and Afghan War veterans now, about about one in six of those discharged needs VA health care assistance. The Iraqi toll has been orders of magnitude greater. We have financed almost all of it with debt, much of it from China. Our military is weaker as a result and we have created a new generation of America hating terrorist. The fig leaf raft of allies we started the war with, a "Coalition of the Willing" has mostly either left or is in the process of leaving. The U.S. is fighting this war largely alone now.
Iraq is FUBAR. I have yet to see a convincing case that staying a lot longer will salvage the situation. Our departure may speed up the conflict, but our presence has not prevented a slow motion civil war.