Well, since we really have not followed the "pre-emption" doctrine yet in Iran, I do not see how this would be a "crushing setback". Pre-emption, I thought, was attacking someone before they attacked us, which since we have not attacked Iran yet, that statement does not make sense.
Secondly, America has only used the UN and Europe to get Iran to stop with the nukes, because we know they cannot touch us yet. While they could bomb Europe with a nuke as soon as they get one. So if Iran gets a nuke, it should reflect badly on Europe, not the US. Of course, Europe still will blame the US, but that will be just shifting blame from their selves, Russia, Libya, North Korean, Pakistan, and China, who have all helped in some small way to get Iran their nukes.
Now if we attack Iran with an actual army, and they still get nukes, I would agree that it would be a setback for Bush.
"“This administration's entire foreign policy, in the name of which we have fought two wars, in Afghanistan and in Iraq, would look hollow,” said Walter Russell Mead (search), a senior fellow for U.S. foreign policy at the Council on Foreign Relations.
“I think it's a realistic threat that Iran could give nuclear weapons to terrorists,” Mead said.
So lets go ahead and attack them to stop that, or lets just let them get nukes so we can criticize the president.
"The nightmare does not end with Iran passing an atomic bomb to terrorists. Iran already has missiles capable of carrying nuclear warheads that could strike Israel and even Europe.
Biden said the tension surrounding Iran nears Cold War proportions.
“It ratchets up everything,” Biden said. “It makes the neighborhood a hell of a lot more dangerous.”"
Not really for the US. The mainland is probably ok, because it should be hard to get nukes inside the border, though Alaska is probably screwed and any interests overseas are also probably screwed. Though many of our major interests are in Europe, so in effect they are screwed by our interests being screwed.
Basically, if Iran gets nukes they are going to use them. Our best bets are to make sure that they cannot hit use and we can shoot down their missiles to protect Europe (We can backcharge them for the service later probably.)