The U.S. has never occupied a country and left, it is just not done. We have over 150 bases around the world in 130 country. We have been a country for 235 years and have only been at peace for 21 years. The budget for 2011 was 664 billion dollars. We are a nation of war, we just don't quit and walk away it will never happen.
As difficult as the situation is, because the US has been involved in Afghanistan for such a long period of time, it will be a longer time before all involvement can be cut. The presence of US troops for so many years has created a situation where total withdrawal has to be done very slowly. It is imperative that there be a good network of internal police and/or troops in place to take over for the US troops before all are sent home.
The United States has spent a huge amount of resources on the war in Afghanistan across more than ten years. If all troops are withdrawn, there is a strong possibility that the Taliban will take over again, and that any gains that have been made, at the cost of many lives, will be lost. The same thing happened in South Vietnam when US troops were withdrawn, causing the entire war to have been a waste of lives.
It is time for the U.S. to withdraw the troops from Afghanistan. It has been to many years of promises to do so and stating that they will as soon as a policy that agrees with America is put into affect, but at this point I think the troops have done all they can.
The troops have no real reason to be in Afghanistan anymore. There presence there not only upsets the local population, but it also has sucked up a huge portion of the American budget for the past years. If there was any desire, or benefit to being in the region, it is long gone now.
I do not believe the United States should leave some troops in Afghanistan. I believe we should pull 100% of the troops out. I do not believe there is a valid reason for us to remain. We have accomplished all we can in this area and there's no need for us to stay.