Some thoughts:
If OBL had nukes he would have used them by now.
They seem to be on a low budget judging by the methods that they've employed.
But if they nuke a city or crop-dust a city with Anthrax, the American public will make it impossible for the President not to nuke something. My first choice would be Medina, followed by Mecca. But I think we'd target Baghdad.
I think that Hussein is spoiling for a fight and that he's behind these anthrax attacks. But I think that Hussein is torn. He desperately wants to attack america, yet he knows that a frontal attack will result in his anihilation. So he will ratchet up the attacks and bluster as high as possible, without prompting a military response. But I also think he has a death wish. And once he gets to the "breaking point," he won't be able to restrain himself from pushing through it.
I say "On Earth," because fear of our God's disapproval might well keep US leaders from using nukes on a large scale, but nothing on Earth would.
Also, I limit it to "nation" that helped Osama get nukes, not merely a few people who stole some nukes as free-lancers. Russia might be negligent in the way it guards its nukes, but would not be culpable in the same way that a country that actively help Osama obtain nukes.
Russia, et al, and China, are afraid of their own Islamic separatist movements. They would complain if we used nukes, but they would not feel feel a need to retaliate on behalf of the nuked. Their governments would quietly cheer.
Pah. We'd get more of that "religion of peace" bravo sierra while the gubmint tightens its grip on the citizenry through "sweeping anti-terrorism legislation". The Dems would be crying about the morality of retaliating in kind against Islamic population centers while Americans are dying of radiation poisoning.
If I'd been in charge on 9-11, every Muslim city from Morocco to Pakistan would have been burned to radioactive slag by 3 PM Eastern time.