Then let's not talk as if Iran had or was likely to have the atomic bomb in the coming 10 or 15 years.
That's one possible scenario. I've made no predictions. Whether that happens or not is a separate issue from considering the ramifications to the region's balance of power if Iran were to gain such a capability.
Let's avoid the demonization and the paranoia that led to the invasion of Iraq under false pretexts...
Contrary to the way some of our newspaper try to depict the Iranian regime (just have a look at my previous argument with MSgt), they are not monsters (but yes, they are a dictatorship) and they are not irrationals. As I have said before, if nuclear detterence has worked with people like Mao or Stalin, it will work with the Iranians too.
I don't believe I have demonized Iran. On the contrary, I have argued on numerous occasions against U.S. military action against Iran, as I believe the overall costs would exceed the likely benefits. Moreover, I still believe that sufficiently strong sanctions coupled with aggressive diplomacy leaves opportunities for a diplomatic outcome, though the present sanctions regime does not approach what I believe would be needed to change Iran's possible nuclear trajectory. Finally, should sanctions + diplomacy fail, I believe an effective deterrence regime could be constructed. If I believed Iran's authoritarian regime were irrational, then I could not argue for the possibility of deterrence. Deterrence would fail against an irrational actor. I don't believe that is the case with Iran.
Nevertheless, it is a reality that Israel by virtue of its being a tiny state and in far closer proximity to Iran than the U.S., has a different risk threshold than the U.S. Even if Iran were to develop a modest nuclear arsenal, the U.S. would be relatively invulnerable (that limited arsenal would not pose an existential threat even if it were somehow used against the U.S.). Israel, on the other hand, could effectively be destroyed by perhaps as few as two sufficiently powerful nuclear weapons. Moreover, an Iranian nuclear umbrella could given Iran's non-state proxies/allies cover to act more aggressively against Israel. For Israel, the likelihood of threat (be it via limited warfare through proxies or a nuclear first strike) is greater than that posed against the U.S. and its margin of error is far smaller than it is for the U.S. Hence, while it might be rational for the U.S. to refrain from preemptive military action, it might be rational for Israel to do so. If, in fact, that's the case, then the emphasis needs to be focused on providing Israel with sufficient assurances so as to find it unnecessary to launch a preemptive attack. Severe sanctions coupled with aggressive diplomacy that generates concrete results would be helpful. Failing that, a commitment to a robust deterrence regime might suffice.
Furthermore, a change in the Iranian-US relations is possible. In fact, as I have already said too, they have tried to make a deal back in 2003, and again in 2008 and 2009. The 2003 deal was about allowing IAEA inspections everywhere in exchange of full access (which is a right) to civilian nuclear energy (which is needed by Iranians if they want to export their oil).
IMO, a diplomatic arrangement that allows Iran a civilian nuclear energy program in exchange for a robust verification regime/safeguards is viable. While some Iranian diplomatic moves have been made, I believe they have fallen far short of addressing verification/safeguards e.g., Iran would be able to possess a sufficient stock of enriched material that could, if Iran desired, be weaponized. A smaller store of such material and strong verification would address that issue. That's why the Turkish-Brazilian proposal, even as terms were not dissimilar from an earlier international proposal no longer sufficed. By the later date that the Turkish-Brazilian instrument had been accepted by Iran, Iran had increased its stockpile of enriched material albeit not enriched to a weaponized extent.
Iran is not a crazy country that wants to impose the Shariah everywhere, it may be a dictatorship, but it has proven that it could also be an ally, for example when it cooperated with the USA in Afghanistan.
Iran, like any other sovereign state, has interests it seeks to pursue. On Afghanistan, Iranian and U.S. interests are not too dissimilar, at least with respect to Al Qaeda. But there are vast and basic differences in interests, too, and those differences create genuine tensions. Furthermore, that Iran may well desire to become a great regional power (and I believe it does) is not "crazy," but that development, too, conflicts with U.S. interests (unfettered access to Persian Gulf oil) and those of U.S. allies in the region (security of Israel + moderate Arab states).