Which other countries will build nuclear weapons if Iran acquires one?
Sooner or later every country will have nukes, and we can’t afford to go around bombing them all back to the stone age, nor should we. Think of it as mutually assured destruction (MAD), the same thing that stopped the US and the USSR from bombing each other during the cold war. The best way to assure our safety is to make friends in the world and keep a strong defense at home — with the operative words being “at home.” Iran isn’t going to nuke Israel because they know if they tried ALL their people would be wiped out. Even if we didn’t nuke them, which they know we would, the fallout would kill them, they’re so close. Sending a crazy person somewhere with a bomb strapped on them is one thing. Wiping out your entire country is quite another matter.