If countries are like people and people, regardless of intelligence, have the right to bear arms, even though they can and have killed others, why can't every country bear nuclear weapons? Either every individual actor, be they person or country, has the right to bear arms or they don't.
Guns are of course not like nuclear weapons; guns can completely kill other people whereas nuclear weapons have far greater difficulty completely destroying other countries. This comparison is made between similar actors, comparing countries with countries and people with people. Whereas a person can shoot and easily kill another, a country would find it logistically difficult to destroy another country with a nuclear weapon. On their respective levels, in comparing the lethality to other like-entities, guns are far more dangerous in the hands of people than nuclear weapons are in the hands of governments.
While Americans enjoy their constitutionally protected right to bear arms, a right to potentially annihilate another entity like themselves; they oppose Iran having a similar right in relation to other countries. It seems contrary on one level to grant individuals the ability to possibly completely destroy each other while on a different level to deny an individual actor, Iran, an ability to at most possibly injure another.
It could be argued that the right to bear arms should be strictly interpreted as an American right, however such a suggestion must be reconciled with the Declaration of Independence which had the American founding fathers affirming, "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights."
Some may worry about Iran and every other country having a nuclear weapon; but if any nuclear attack was to occur on one of the almost 200 countries in the world, it would be unlikely to be completely destroyed. However if a person attacked another with a gun he or she would most assuredly be killed and yet in America everyone retains the right to bear arms.
It would appear then that Americans allow individuals greater rights to possibly kill other individuals than they grant other countries the right to destroy other countries. And that may appear valid in the utilitarian measure of things as rights might not deserve to be scalable, however as individual people are more likely to commit acts of violence between each other than countries are, especially since Americans with mental-health issues can obtain guns, it would appear that it is not just countries that shouldn't have this comparable right, but that people shouldn't either.
In denying Iran a nuclear bomb because it might use it, Americans need to explain why they allow weapons to be given to citizens, especially those with mental illnesses, who, at least a few, will most assuredly use them to kill others.