> There is no conceivable way that terrorists threaten our national existence/security.
This statement surprises me. Especially your talk of casualties. I think you miss something important about "terrorism". It is far more than raw casualty numbers. It is about the "fear and uncertainty" they generate in a populace. And that, to me, is a threat to any modern nation's existence, in a world whose economy depends a lot on things like "confidence" and "optimism".
Perhaps I misunderstand developed nations, but from my point of view, your statement seems alarmingly absurd.