What is there to win? The U.S. is not fighting an army, but rather an idea.
The U.S. will never be able to say they won the war, as there is no formal group to say that they surrender. The U.S. is fighting "insurgents" from all over the region who are fighting for them to leave, therefore as long as the U.S. is on their soil, I doubt that they will ever give up the fight, as in their mind, they are fighting off an invader that is on their land.
While on the other hand, the U.S. cannot continue these wars, even if they wanted to. These wars are costing literally trillions of dollars. We will have collapsed economically before we can say that we defeated a bunch of "insurgents".