Probably due to the lack of information/internet/etc. We see everything brought to us by satellites and DSL, all over the world, all at once. It's not like they have North Korea, Cuba, Nigeria, India (well, except for Pakistan), and China constantly attacking them. That's the difference I think...

Which could work if the enemy is finite, but each attack forges new enemies? What's the solution? I think there are problems where throwing all the resources in the world at them won't solve anything. Better to entrench, spend the money on better defenses (instead of offense/campaigns), better security measures, etc.

I'm not excusing for a minute their behavior, I'm just trying to understand the behavior of someone that may not be directly involved with "terrorists" that observes one constant/repeating force that is blowing stuff up. What happens over time?