Do you know that Bush administration allowed Al-Qaeda Network to slip into Pakistan from Tora Bora sector? An American commander on the ground requested reinforcements from his higher ups to eliminate Al-Qaeda Network in Tora Bora and his request was denied. Imagine this.
Pakistan simply chose to safeguard its interests vis-a-vis Afghanistan and weather the storm. Duplicity my foot.
Americans mainly saw in Afghanistan an ideal environment for experiments (e.g. Drone warfare), and to gather vital information from Afghanistan's neighborhood.
If they want to win a war, they can and will. Any irregular warfare force cannot defeat world's greatest army in the battlefield - nope. Americans should be questioned about their true mission in Afghanistan.