Iran is only the “number one supporter for global terror” if you think the State Department list of terror organizations is accurate, which its not. There’s plenty of US-backed terrorists, we just call them “rebels” and “guerrillas” because they’re on our side. If you do the same shit as those rebels and guerrillas, but outside of US interests, you guessed it, terrorism.
Also, being nuclear-armed statistically makes a country much less likely to go to war. Look at India and Pakistan, they used to fight all the fuckin time, they both got nukes, and now they hesitate to go to war with each other, even when tensions reach the hottest point they have in decades between them.