From a recent interview with Noam Chomsky:
Q: Was the US right in invading Afghanistan following 9/11?
Chomsky: I felt that was a major crime and still do. The United States invaded Afghanistan for a very explicit reason. It was made public, but there has been a lot of lying about it since, but it was very public. The reason was that the Taliban- the Bush Administration demanded that they hand over Osama Bin Laden to the United States and they asked for evidence of his crime. Well the Bush Administration wouldn't provide any evidence so they invaded. The reason they didn't provide any evidence, it later turned out, was because they didn't have any. Eight months later the FBI conceded that after the most major international investigation in history, they simply didn't have any evidence. They believed the plot for 9/11 was hatched in Afghanistan, but was probably implemented in the Arabian Peninsula and in Europe.
So they invaded, and they invaded with the knowledge that they were putting several million people at risk of starvation. They were right at the edge of starvation and an invasion might have driven them over the edge. Their estimate was 2.5 million people. In fact, the aid agencies and others were infuriated by this and they had to pull out their support and so on. Fortunately the worst didn't happen, but to carry out an invasion on that assumption, when your sole goal is to get the government to hand over somebody when you can't provide evidence is just a major crime and the invasion has had a horrible effect on Afghanistan. Some of the current studies of public opinion reveals that one of the most popular figures in Afghanistan right now seems to be Najibullah, the last Communist ruler of the country after the Russians had withdrawn. Since then the US has turned the country over to warlords who tore it to shreds, then invaded, and now the country is heading towards disaster.
As for current policies, I think Obama looks more aggressive and violent than Bush. The first acts to occur under his administration were attacks on Afghanistan and in Pakistan, both of which killed many civilians and are building up support for the Taliban and terror. He wants to extend the military side of the war. There is an Afghan peace movement, which is calling for a reduction or an end of terror. President Karzai has pleaded with the United States not to carry out attacks that will hit civilians and, in fact, has demanded a timetable for the withdrawal of foreign forces, American forces, but that's just totally disregarded and the opportunities for a peaceful settlement are just ignored. There are reasons for that I won't go into, but I think it's a terrible policy. They're ruinous for the Afghans and maybe for the Americans as well. It's also spilling over into Pakistan, naturally, which is really dangerous. Pakistan, by now, is partially under the control of the radical Islamist elements that Reagan helped install there. It's an extreme danger for Pakistan and actually for the world, since Pakistan has nuclear weapons... (link)