I don't think it is possible for terrorists to defeat us militarily, but than can defeat us economically.   By destroying our economy (as 9/11 proved) our whole system can collapse.    A collapse of the US economy would trigger a world wide depression.   (just look at the effect our stock market has on the world)    A world wide depression enalble terrorist to gain more foothold without as much opposition.   It is there only successful strategy.

The the person who quoted the word "bananas".    In the energy industry we use that word to describe our current policy.   We have gone from "Mimby"- not in my back yard to "banana" Build absolutley nothing and never again.

It is scary how fragile our power infrastructure is and how little it would take to disrupt it.