Frankly the concept was good. It was the execution that was lacking. If superman wanted to end the threat of nuclear war. He would have to take them by force. Which would be pretty interesting. But to be fair the story dose kinda fit the Pre-Crisis Superman.

The whole idea is stupid and makes Superman looks like an immature idiot. He is a 30 or 40 years guys who hasn't figure out what most 20 years old would already have. There was no 3rd world war because of nuclear weapons.It's called balance of terror and you learn that in high school.

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This movie delivered a strong moral message:
Superman wanted the world to be united. He feared earth will suffer the same fate as Krypton. Earth is Superman's home so he decides to rid the world of all nuclear weapons to avoid a nuclear war.
Thats a Superman character trait.

Not to mention its possible the only reason those peaceful nations weren't already at war with each was since they had nuclear weapons they couldn't risk fighting each other.

What could they do about it? None of them could stop Superman!