Nobody asks for a quagmire but that is what it was always going to be once US troops step foot on their land. You asked for them to go in there full force, unearth the terrorists and guess what? It was the entirety of the government and countryside ruling leaders of townships.
So you asked for what the US infantry could not provide you in a short and timely manner. The entirety of the government of Afghanistan was replaced with general elections and to walk away just means the nation falls back into radical control.
The Afghanistan realigned armed services had to be trained how to handle their own internal Al Queda crisis. The hotspots had to be nuetralized and the target you wanted eliminated changed locations. Each location requires time to asses and execute a battle plan.
What you really wanted is the US to kill a lot of people to balance the scales. Not to execute a long term plan, just kill, kill, kill and then walk away once you thought the body count on their side was reasonable to say mission accomplished. That is not a solution, it is just revenge.