If a Nuclear bomb were dropped....

[Pat Mustard]

Yeah.  The U.S. would pick one country as scapegoat for "harboring terrorists" and go after them, provided they have oil.

That's what happened when a single building went down. I'd imagine a more extreme reaction from a whole city being destroyed.

Well given the only possible suspects are countries the US has allied with for years and Russia, it'd be scapegoat all the way. The idea of a private group developing usable nuclear weapons is fairly preposterous without state support (the so called dirty bomb, wrapping nuclear waste around a conventional explosive is a no go). Aum Shinryokyo (or whatever the fuck they called themselves) spent years to try and build a bomb and couldn't even with billions $ at their disposal and some competent physicists.