I think a lot of perspectives have been messed with. What was the biggest killer of Americans in September of 2001? It was automobile crashes. We lose about 3,536 Americans per month due to car crashes.
We did not declare war on GM or Ford because of this. We decided that 3.5k deaths per month is an acceptable loss to travel around quicker.
Likewise, when it comes to crime, we don't spend all our money trying to stop it. We spend some on heath care, education, improving roads, etc. We have found a rough balance in crime prevention and our other desires.
The worst thing that could have happened from 9-11 was for people to over react, develop fear and act irrationally. Unfortunately, it seems that is what happened. For example, people were so scared to fly or were so inconvienced at the airport, that more people drove cars.
Cornelle University estimated that the deaths from the extra people driving resulted in an additional 1,200 deaths.
I would bet that if 9-11 had not occurred, we would not have had the war in Iraq. Bush rushed into the war and pushed the inspectors out because he knew he would lose political capital if he waited too long. And we see how badly things are going in Iraq now.
In the end, we have wasted billions of dollars and have made the world a more dangerous place. If we had stayed in Afghanistan and worked to make it a better place, I think the world would see Americans in a better light. Now we are seen as a belligerent country and we have empowered the fanatics with this view.
Terrorists did spread terror on 9-11. But 5 years has allowed for people to calm down and accept a new post-cold war world. If there is ever another major terrorist attack, I hope we keep it all in perspective and remember the lessons from 9-11.