This is basically another Munich situation right here.

Iran has backed down from a nuclear deal that would have significantly eased American tension with them. The deal was to send Iranian low-enriched uranium abroad to be enriched up to reactor-grade.  While this first seems odd, the crucial point is that currently their uranium is in the form of uranium hexaflouride, a gas that can be endlessly enriched up to bomb-level purity.  The uranium enriched abroad would be returned in the form of metal fuel rods, and impractically difficult for the Iranians to turn into bomb-grade material.  Darn…it sounded like a good idea.
It seems as though there’s little that can practically done to stop the Iranians from getting the Bomb if they want it badly enough.  But for them to agree and then back out of this deal makes no sense, unless they just needed two weeks to put together a weapon.  Which isn’t the case, obviously, it seems like a stall for time that didn’t put them in a stronger negotiating position and needlessly antagonized the Americans.  So that was kind of bizarre.  Bizarre or not, however, the Iranians are still rational and there seems to be no actual reason that Iranians with the Bomb couldn’t be deterred just like the Soviets.  Their principal adversary is a regional power with nuclear submarines and in all probability more nuclear weapons than China.
Given all that, I’m pretty sure the actual aggressor in the U.S.-Iran relationship is not the Iranians.  They clearly don’t like us, sure.  But in Iran, I’m fairly sure that political discourse does not revolve around near-daily discussion of how and when to best attack the U.S.  If I were the Iranian government, I’d damn well want a bomb, if only because it seems like America is willing to invade anywhere that looks as them funny, if they don’t have nukes.  And give actual nuclear states a wide berth.