Comment by Epa095

No, Ukraine is not the (sole) reason. USA has been in multiple wars since 1945, and never used the bomb again. They know the value of the nuclear tabu, and are not interested in breaking it, independently of the situation in Ukraine. They also have enough conventional weapons to level Iran with those, so they dont need to use nukes.

In addition I would hope that even in the morally bankrupt state USA is in today, murdering 92 million people would cause some political problems (but this might be naive of me).