They have an intimate knowledge of the terrain of the religion, the Taliban militia has experience fighting the old Soviet forces in the same places.
They currently have the advantage of numbers.
Yes, their equipment is outdated, yes the US has greater economic might. But since when did this stop people resisting the US and it's lackies? remember, Che held out for almost 2 years in Bolivia against superior numbers and technology, and he didn't even have support from the majority of the people there. Guerillas with support and resources (remember, the Taliban can rely on a LOT of funds from groups like Bin Laden's), and especially experience, can do a hell of a lot.
If the US goes for all out war in afghanistan it will be another Vietnam, you can bet on it.


