Lots of good points on this thread. The question of what the US objective should be has been answered several times, and it is not to bomb Afganistan back into the stone age, they've already absorbed enough superpower s*&t.
I know it will not make a difference to those who have already decided the US is the big bad boogieman but have a good look at the food going into Pakistan and Afganistan to feed people, a lot of it has stars and stripes on it. That is the real way you do things over the long term. You talk to people, learn about them, let them learn about you, live with them if at all possible and if you can not you build a big fence and agree to stay on your own side. People in the US know that the average Afgan just wants to be left alone to live his life like anyone in New York, London, Peking, Bombay or anyplace else, and there is little future in turning the place into a glowing hole, which the US could do at modest cost many times over whenever desired.