Over seven years ago, the United States was successfully attacked by re-routed American airliners, flown by suicide hijackers under the direction of Osama bin Laden. The attacks caused millions of dollars in damages, and thousands of American lives were lost. Osama bin Laden and the other perps of the 9/11 attacks were traced to Afganistan. When we asked the Taliban government to send them over, they replied "Come and get them yourself", so we did. Within a couple of months, we had Osama bin Laden almost trapped - but slight shortage of troops let him escape.
Since then, the slight has grown to large (Iraq has drained them away), the Taliban have regrouped their armed forces (just like the Afgans did for the British and the Russians), and they have changed from opium outlawers to opium enablers (so heroin addicts in the United States no longer have to worry if tomorrow's fix is available, they just worry how to get the pusher money.). The war we should have won seven years ago has become a stalemate. (We control the cities, and the places where we are in the countryside; the Taliban controls the rest.)
President George W.Bush still hasn't given a good reason that stands up for our Iraq invasion. The Weapons of Mass Destruction (WMD) turned out to be not nuclear (the Iraqis were years away from a nuclear device), not biological (no nasty developed bacteria were found) and not chemical (the leftover poison gas containers from the Kurdish insurrection were found rusted out and nonoperational). The intelligence officials who supplied Bush with this bogus data have been not fired swiftly and publicly, but rather retained or promoted to cushy posts (such as UN ambassador). Also, the goals and objectives of our Iraq occupation have been unstated, so we have no idea when the victory parades will be held (and a newly-constructed billion-dollar embassy was built for a long stay). (One objective has been achieved - the large international oil companies, which Saddam Hussein expelled from Iraq, have returned on Bush's invitation.)
Therefore, I can only conclude that there are three reasons left for our continued presence, which Bush has not recently mentioned:
1. The resolution of the Bush-Saddam Hussein family feud. This part of the mission has been accomplished. Saddam Hussein and his two sons are now dead, and any further family members have disappeared.
2. The re-establishment of international oil companies for looting Iraqi oil deposits (at, of course, a fair price - but the cost of extraction for Iraqi oil is around $1/barrel, vs. $25/barrel in Texas).
3. The prevention of attacks (like 9/11) on American soil. For this, Bush established an anti-American honey pot on the other side of world. If you hate America with such a passion that you are willing to die in direct battle with Americans (there are those type of people, and Bush hasn't done anything to decrease their numbers), you now have, with a convenient commute, easy access to battle-ready Americans who say "Bring it on!".
So far, the jihadists have taken up the battle offer in Iraq, and left the American mainland alone. If we leave, they will have nothing left but the American mainland to attack, and we can't have that, right? Besides, who will protect the international oil companies who have set up business in Iraqi oil extraction under American invitation? George W. Bush's trillion dollar vanity war would go on anyways, because the Chinese are lending at a good rate, and the Democrats would just spend the money on socialistic causes, like health care, Social Security, etc.