Nation building has hurt the U.S. in Afghanistan
As President Obama prepares to tell us how many troops he will withdraw from Afghanistan, it's worth pointing out that the U.S. was never supposed to a launch a war against Afghanistan. It was supposed to be against several hundred Arabs and a hodge-podge of other nationalities who had taken up shop in Afghanistan to plot terrorist attacks, plus a slice of the Afghan population that thought sheltering them was a good idea. When the Bush administration largely accomplished that in early 2002, it decided to snatch defeat from the jaws of victory by turning the war into a quest to give Afghanistan something it had not had in decades: a stable government.
This was a classic example of moving the goal posts, and it has been costly.