They aren't all combat troops, either. Many are civil engineering troops helping to rebuild Afghanistan's shattered infrastructure. Others, as illustrated on Dan's recent linked article on MedEvac troops stay busy in Afghanistan, are providing medical care to Afghanis.

Many other countries pledged money to help rebuild Afghanistan. How many have actually ponied up with the cash? Just because something needs doing, it doesn't mean that we're the only ones that must do it. Can't other countries help relieve humanitarian suffering, or is their role limited to morally superior posturing while doing nothing to eliminate tyranny and relieve suffering?

The article I linked mentioned all those UN and NGO "experts" running around the countryside. The US pays about 25% of the UN's annual budget, so we're paying for a lot of that, too.