I think you're underestimating the impact of 9/11 here.
Look what it did. Not just that day, but since then. Granted, most of it self-inflicted overreaction, but yeah.
You're missing my point: after 9/11 we pointed the cannon at... Iraq.
If some ISI guy allows an AQ buddy to smuggle a nuke into NYC and it detonates, I'm finding it hard to believe we'd simply obliterate the entire country with nukes.
That's not even the best part. The best part is that Pakistan has nukes because we decided in our infinite wisdom to look the other way when Pakistan started acquiring them because we were so obsessed with sticking it to the Soviets in Afghanistan as payback for Vietnam.
And now we're bogged down in... Afghanistan.