Why do you believe that Americans are unwilling to kill other innocent Americans? Why... when thousands of Americans kill thousands of other innocent Americans every year... do you think these murders are like, "Wait a second... I can't kill you... you're my fellow American."
Here's the problem... if you are a good person (which I would hope you to be) a patriot and an honorable man... than I can understand how it might be hard for you to believe that people are capable of murdering innocent people, whether foreigners or their own countrymen... for sheer profit and greed. Nonetheless, do not project this good-heartedness onto others (especially the extremely elite and powerful) for that is naive of you to think that other people can't be filled with this heartless cruelty...just because you're not. Some individuals will kill any and everyone (regardless if it's their own countrymen) if it brings them more wealth and power... and that's a well documented fact throughout history.
Politicians (democrats and republicans) are the scummiest people on the earth. I'm not saying that if you have political beliefs associated with these parties that you are scum... and, I'm not talking about conservative and liberal beliefs per se... I'm talking about the elected individuals (politicians) who manipulate the American people and their morals and values, by projecting this phony image in the media... that preys on their good-heartedness.
The most powerful men throughout history have always been the most barbaric... it has been that way since the beginning of time and it will continue to be that way... And, if that's true... than why can you believe that rulers from other countries will murder their own innocent people, but can't believe that elements within the USG are willing to kill its own people?
I think you are blinded by your patriotism...but, trust me - these men responsible for 9/11 are not your fellow countrymen...nationalism means absolutely nothing to them... they only answer to two things, and that is money and power.