The US and allies should withdraw from Iraq because Iraq is a strong country. The people in the country are relatively modern compared to other countries like Afghanistan and Iran. They are ready to lead themselves. The various factions groups in Iraq are able to get along with relatively little conflict.
The entire proposition of the Iraq war was flawed from the start, as is now known with the widespread availability of facts on weapons of mass desctruction (WMDs) and their nonexistence in Iraq. We should remove our troops as soon as safely possible, so that both countries can get on with their lives.
I believe the United States should withdraw from Iraq, our allies should make their own decisions. I do not think their is a valid reasons for us to stay there and I do not think we need a base in the immediate area. Out presence wasn't needed in the first place.
What Iraq needs is a strong government that is able to forge a peace between the two groups who are fighting. It does not have that strong government yet, and if the United States withdrew now the parties would be fighting more intensely. The USA can't pull out of Iraq until the country is able to establish some cohesion.