It provides the underlying motivation for the govt to stage an attack on its own people, its happened before.Its been done many times thru history, usually works too.
We have an energy crisis, it isnt bad now, but it will be.The countries we depend on for oil are unstable politically, a war on terrorism is an excellent excuse to use to move in and take control.Look at Iraq, ya saddam was a real SOB, but from a military standpoint he wasnt a threat, never was either.The economic sanctions really put the hurt on that country, thier military was a paper tiger.Iran will be next, maybe saudi arabia too, problem is with saudi arabia though they control about 1/3rd of our economy and have a 2:1 debt to income ratio and the oil is running out.......that isnt good.
What 9/11 did was provide a never ending excuse to continue to use our military whether its warranted or not, and gives the US an excuse to move into the unstable oil producing nations.
Take serious note that one of the FIRST things the US did when the Iraq war switched into the mop up mode was oil production was a top priority.The war is still raging there, yet the oil fields and pipelines are a big priority.If the US was there to restore some semblance of order and help them regain control of their country and become a peaceful productive nation, that's the last thing you'd focus on.