I've mentioned this before, but the US does not have the power to end the war in Afghanistan. That was going on before 2001. The only thing it can do is remove its own involvement. There has been a civil war in Afghanistan since the 1970s. The only thing that will happen if the US decides to leave is that Iran and Russia will fill the vacuum, just like they did in the 1990s when they were pumping support into the Northern Alliance.