Atabuy,
It may surprise some but I don't subscribe to the 'Iraq equals Vietnam' analogy. In Vietnam we were attempting to keep an (ostensibly) external force (North Vietnam) from taking over an (ostensibly) independent nation (South Vietnam) whereas in Iraq we are the external force.
In the larger scope we were attempting to prevent the spread of Communism and it is possible that by our sacrifice we indirectly did so, whereas in Iraq we are trying to stop the spread of nothing. Nowhere in the world were Baath Party cells springing up or Peoples Liberation Fronts swearing allegiance to the Baath creed.
Our rationalization for attacking Iraq was the strategy of preemption but events have proven that the 'evidence' used to justify the act was at best erroneous, at worst a criminal fraud. If premption is our strategy then a far stronger case could have been made for invading Saudi Arabia - (funding terrorists, providing manpower); Pakistan - (providing training centers for terrorists, conspiring to distribute WMDs (nukes) and harboring terrorists); or North Korea - (multiple WMD offenses). Instead we chose a nation that, while an enemy, was a relatively minor threat.
While we have succeeded in removing Saddam Hussein, what have we created? Jeffersonian Democracy will not spring forth whole from the Iraqi soil nor will centuries-old religous and social grievances be set aside. (Just because they hated him doesn't mean they like us or want our help.) In his place we will leave uncertainty and we may well leave Iraq worse than we found it. We forget that not everyone wants to be like us, live like us or wants the social upheaval our way of life would entail for them.
All this and none of it effects Al Qaeda negatively in any way - indeed, their recruiting is up. Meanwhile we must be careful what we create in Iraq - keep in mind we created the core of Al Qaeda to fight the Soviets in Afghanistan. They say the path to hell is paved with good intentions and this is, in many ways, an illustration of the unintended consequences of those good intentions.
The war against terrorism is not a new one nor is the use of terrorism against the U.S. new. (However, when the Federal Building in Oklahoma City was bombed we did not attempt to nullify large portions of the Constitution with allegedly necessary laws passed under the guise of 'patriotism' nor did we invade Iraq.) The fact is that we underestimated our adversaries and we allowed ourselves to be lulled into a sense of security that was only an illusion. Remember, under the rules in place on 9/11/01 the box cutters the terrorists carried were permitted, as were the various penknives and pocket knives we took for granted and took through security.
I don't have all the answers but I do know that invading Iraq wasn't the even addressing the right question. Our real enemies are not of the sort we can fight with armored divisions or fighter wings; however, if we must fight them we can fight them on their own terms and succeed. Unconventional Warfare forces, for instance, have repeatedly proven an effective means of dealing with such organizations. The ability of such forces to operate in varying strengths allows us the speed and flexibility necessary to defeat terrorists and when coupled with a real and effective intelligence operation would allow us the preempt and eliminate those who threaten us.
Unlike many I don't blame Bush for not being ready on 9/11 because none of us were. I do, on the other hand, blame him for his actions after 9/11; his actions, in the arena of foreign policy, have only helped create more terrorists while expending the post-9/11 goodwill of the world. Meanwhile his sadly misnamed 'Patriot Act' has done more damage to the Constitution than any law since our nation was founded.
We will always have enemies but it is not necessary to change the very nature of our nation to defeat them. In fact, by making those changes we give them a victory.