All the "why us? and "what do these people want?" talk is beside the point. There will always be some deviant group seeking to get their way. Furthermore, as long as fame is our key currency, there will be a ready supply of hopeless young man to do their bidding.
They might not all come from the Middle East and their targets may not be the same ones but they'll be there. The damage they will cause and the pain they inflict will get steadily worse. There have always been homicidal maniacs. Now we have suicidal maniacs, which is worse.
The availability of cheap communications technology means the terrorist will always be just slightly ahead of the authorities. That's another thing you can depend on. As Stanley Baldwin said long before the last war, "the bomber will always get through".
In the light of this our talk of destroying the threat is as empty as their carefully blood-curdling rhetoric. The best we can hope is that this is contained rather than extinguished.
The price of that containment will be some curtailing of the things to which we have only recently grown accustomed. Easy movement across borders is one. Unlicensed communications platforms is another.