Things are not that simple. America did not care about Europe until it was itself hit at Pearl Harbour. So please spare me the crap about US being a benevolent country being on a mission. Like any single country it veils its self-interest in ideology, here patriotic and religious. Note that I don't want to draw any parallel about the current event and Pearl Harbour. I was just talking about America in WW2.
I'm sure that you will agree, that it is a tactical victory for a country to expend 18 people in the future.
Like America, many countries in the name of RealPolitik breed all sort of evil armed and subversive groups. America has the power to do it outside of its own territory so its leaders think it will not to much affected it this backfires. But this snake breeders sooner or later are proven stupid. Tracking in the past the financial backing of the islamic nebula, if America had to do massive retaliation on all these backers, it will have to bomb itself. Anyway I am sure that the countries who breeded these terrorists are ashamed and embarassed. It is against their own interest that the consquences of their actions eventually took a so massive and gruesome proportion. Unlike Bush said, this will not be a war until it is proven that the head of a government decided to wage this attack againt US or Bush decides to hit a country he deems responsible of this attack.
I just hope that the XXI century will see the dismise about idelogies like aggressive religions and nationalisms when we ultimately realize we live in the same very small planet.