system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it ok for the U.S. to have nukes but Iran can't?
gpt
Short answer - we don't want anyone that doesn't already have nuclear weapons to get them.  The more countries that have them, the greater chance that one will get "loose" and used by an independent actor.

Of course, we'd also like some countries that do have them to get rid of them.  But once you have one you get a lot of leverage (which is why countries want them in the first place) and it's hard to go back.  So we spend a lot of time negotiating treaties on arms reduction.

Thirdly, if a country is going to have them, we prefer that it be a friendly ally with a stable government.