Don't forget that those 19 hijackers gave their lives for what they believe in, no matter how far away from our frame of mind theirs may be. They gave their lives in pure hatred for the US and it is how the US is perceived that needs to be remedied in order to stop the bloodshed. As to how this is best achieved is up to individual belief, but personally I believe that the invasion of Afghanistan both weakened the terrorists abilities and strengthened their will. This in the long run will not benifit the US.
Almost all countries are hypocritical in their foreign policies and the way forward is to admitt this and seek to make decisions with all people in mind.
That's my two inches of ivory.
