The Taliban hit the US in their weakest spot. The massively sophisticated machinery of the US is extremely expensive to buy, and to run. With oil now at 120$/barrel. its eating up American citizens. If I was a US general, I would get massive numbers of poor Christians from Africa in US uniform, to form a low-tech army and occupy the villages. Of course, this would have unintended political consequences. And anyway, the US just couldn't win because the Taliban are fanatics and will willingly die for the cause.