Why do Americans think their war OF terror is just?

Whats so righteous about invading a foriegn country, that posed no threat to you? And I dont want 9/11 used as an excuse, because even if the USA governments 'official' version of events is correct, its still unfair to invade & blow up a whole country....and we cant even say what REALY happened anyway, there are far too many unanswered questions- which is reasonable doubt. I dont want to hear Saddam used as an excuse either, because he was around for a long time before America took any action. How would you guys feel if some country didnt like your system of government, and were richer than you? How would you feel about them tapping into your water supply, setting up bases & blowing the crap out of everything???