You have a lot of suspicion from the neighbors of Afghanistan about U. S. intentions. Iran is already, to some extent, trying to undermine the U. S. in Afghanistan. Russia is now becoming increasingly nervous about a more permanent U. S. presence in Central Asia. And China is not keen that the U. S. should be so close to its borders over a long period of time. Certainly, if the U. S. is going to be there for a long time, it's going to exacerbate regional tensions.
It's astonishing how much trouble one can get oneself into, if one works at it. And astonishing how much trouble one can get oneself out of, if one assumes that everything will, somehow or other, work out for the best.