The right course would have been for the U.S. to destroy all the significant facilities in Iran's nuclear weapons program from the air, and also all the sites where its ballistic missiles are produced and deployed. A small fraction of this country's air power could have done that quickly and effectively, without much risk to our forces and without killing many civilians. And the U.S. should have struck quite a few years ago. Iran could not have done much to retaliate in any case. And if the jihadists who rule it had been warned that any attempt to retaliate would prompt an even larger bombing campaign against all sorts of other military targets, a blockade, or both, they probably would not have dared try.
Either way, the humiliation likely would have cost the Khomeinist regime its hold on power, leaving the Iranian people free to choose a government that was much better for them, and much friendlier to us. But because we did not have a leader who could muster the public support for this kind of action, the jihadists kept right on pursuing their atom bombs. For fearing to run a fairly small risk, we now are confronted with a far larger one. One of the more dangerous consequences of this shameful appeasement is that it puts Israel in an intolerable position, and one it may well have no way to get out of except by using nuclear weapons.
Israel knows its area and population are small enough that even a single atom bomb set off in Tel Aviv, or maybe some other city, would probably create so much physical, social, and economic damage as to finish it as a nation. Even letting Iran hold that sword held over its head could weaken Israel indirectly, by causing many of its people gradually to become so weary and demoralized that they left for safer countries. I believe Israel will do whatever it feels is needed to avoid all that--even if that means attacking Iran's nuclear facilities by itself. Iran's leaders have been foolish to talk about how once they get the atom bomb, they plan to use it to eliminate a nation that already has a couple hundred of those bombs, with the missiles to deliver them. Regular bombs of two-and-on-half tons may not be strong enough to destroy a deeply buried nuclear weapons facility, but a nuclear bomb of twenty thousand tons would make very sure of it.