In a few short years, it is going to be clear the U.S. has lost their leadership position in the world. Some observers are going to look for triggers, and others for analogies.
The analogy they will settle on is that Iraq is to the U.S as Afghanistan was to the USSR.
Of course, there are going to be clowns who deny we lost Iraq, who deny that the military/financial complex that rules the US right now is responsible for the political and financial mess we are in, who deny any responsibility at all.
However, the denial that the invasion has severely limited U.S. options of all kinds isn't going to prevent the inevitable consequences of the invasion. The easiest consequence to identify of the invasion is the financial consequences.
I'll try this in a different post as one commenter has pointed out I've blown my chance with this post, so I'll just title it
Iraq:USA::Afghanistan:USSR Part II