You're practicing relativism. It matters not one bit whether one American is killed in such a manner or 3,000. It's like the spate of kidnappings for ransom now so popular in Central and South America. Pay the ransom and what do you get? More kidnappings...LOTS MORE! Or more acts of terror and death. The perpetrators must be hunted down and shot for the vermin they are!
If on the other hand, for each and every such act, a Ranger strike team were sent into the area with orders to NOT return with any prisoners such activity would cease....at least insofar as our citizens are concerned.
In much the same way that crimes against the people dropped over 25% when the Florida Concealed Weapons Permit system went into effect in 1987...because criminals aren't into getting killed, they're into making safe easy money.
I am not using moral relativism, just telling you that if we didn't get our act together after 9/11, a suicide bombing isn't going to change anything. I think we do have our act together for the most part.