Killing the enemy isn't happening - we'd have to open gas chambers and run the whole country into them to accomplish that. Ten years of overwhelming military superiority has utterly failed.
So, the Afghani soldiers fighting and dying on our side are 'the enemy'?
Are the relatives of the Afghanist fighting and dying on our side also 'the enemy'? (Two-thirds of all civilian casualties in Afghanistan are victims of Taliban violence).
The fact remains that terrorism on the scale that Al-Quaeda and its allies wished to pursue requires infrastructure: training camps, bases, production of heroin and azurite, etc. These can be targeted militarily, and these can be destroyed. America isn't defeated quite yet.
But I disagree with the previous posters who said we (the West) should never negotiate with terrorists. We should, and do, negotiate with terrorrist groups if we can get them to lay down their arms and incorporate themselves into a non-terrorist future.
This has been done dozens of times before, and every successful anti-guerilla policy in history has always been a combination of 'bribe some of the factions, kill the ones you can't bribe.'
This is how America defeated the Iraqi insurgency, this is how England ruled the colonies, this is how the West can win in Afghanistan.