There is a huge difference in the US today and Japan in 1945. Japan was already beaten and on the ropes but was refusing to surrender.
If Iran nukes us (and that’s a huge if) I predict the American people will be so enraged that Iran will be destroyed. Of course we will have to get the POS out of the White House first which shouldn’t be too hard in that case.
Japan was also a homogenous culture where the vast majority of the population worshiped their head of state as a god.
Yes, we have a little bit of that here in the US right now admittedly. But the response of most Americans to losing a major population center or two to nuclear fire would be breathtaking. If a US President didn’t respond immediately by anihilating the attacker we’d have a quick but overwlmingly popular rebellion, with the full support of a good number of states governments.
After which the attacker would be annihalated by the new government.