An Iran with nuclear weapons is no threat to any country anywhere in the world. For a couple of big reasons.
1. USSR. The USSR was extremely hostile to the United States during the cold war and yet despite their hostility they did not attack any country in the western world. And this is despite the USSR having a larger nuclear arms arsenal than the United States.
Why did the USSR not attack the USA? Because they knew the retaliation from the United States would destroy their country.
Iran also knows this which is why even if the country wanted nuclear weapons they would not use them. Iran knows that if it launched a nuclear attack against any country in the world, let alone the USA, that the USA would literally destroy the country or lat least its infrastructure.
2. Iran has no history of attacking its neighbours. In at least the last hundred years Iran has not attacked any other country. Iran has zero track record of aggression and this is despite the fact that it has been attacked covertly by the United States when the Shah was installed.
So in summary, there is nothing to lead anyone to believe that a nuclear Iran would be a danger to anyone.
To believe that it is justifiable for Americans to spend thousands of dollars per person in order to buy arms from weapons manufacturers to protect against the “threat from Iran” is misleading.
To say that it is worth jeopardising the lives of hundreds of US service men and women for the sake of a paranoid illusion is absurd and is an insult to any service person that is asked to risk their lives.
To believe Iran is a threat is a paranoid delusion ie to believe in something despite the fact that there is no evidence to support your belief.
The worrying thing for the rest of the world is that political leaders of the worlds most powerful nations appear to be suffering from extreme paranoia. It should give people cause for concern that apparently mentally unstable people can rise to such prominence in world politics.