This is (sort of) forgetting the fact that anybody except the US having nuclear weapons is a massive problem, and that nuclear proliferation is a
Jewish Invention. They did create a very real threat to try and (successfully?) force the hand of the US, and if Iran does indeed actually intend to produce a production line capable of producing working warheads to place on their midcap but proven vehicles, (they would need roughly 100 working and hot delivery vehicles for a reliable enough threat of piercing AEGIS&Friends and make it worth their effort), it would make them a power capable of dictating the flow of global politics.
However, Iran producing warheads in the range of 1-10 bombs can really only threaten Israel. That being said, if
real evidence of their ability to produce warheads appears, then the US does have an obligation to stop them. Not for Israel, but because of the responsibility we shouldered when we nuked Japan and took the throne of Hegemon.