Sadly, the history of warfare is that nations rarely learn from their mistakes, a point laid out in the excellent documentary about Robert S McNamara, The Fog Of War.
In my humble opinion, the US shold realise it lives in a democracy, and when their soldiers start to get slaughtered in the high numbers, the emotional power of a nation is to bring them home. It is inevitable that the Democrats, with their anti-war stance from 2004-2008, would be a shoo-in at the next election. Thus is the trouble of democracy, and a example of the tyranny of the majority. (Or in this case, the longing of the majority).
In Bin Laden's latest As-Sahab video, The Solution, this is exactly the point he is making. He compels the world to see that superpowers fall, and it just so happens he has scored an incredible propoganda victory by claiming
'19 men, driven by only their love for their God, changed the face of America's compass'.
I think it is very important to understand that Bin Laden never downplays the incredible might of American military power. His victories are when it is defeated by the ordinary man.
If Al-Qaeda gained a lot of money and could build a nuclear sub, firing up to 20 missiles into America off the cost of Florida, it would not score the same victory as a lone lover of Islam smuggling a nuclear weapon into New York and detonating himself and everyone else, because Al-Qaeda do not go in for sterile victories.