So, according to your rational only America and its allies are allowed to possess nuclear weapons but no other nations? How would you argue if the table was turned and India and Pakistan prohibited the US from possessing nuclear weapons? I believe the world is more complex and complicated than you like to believe.
1. The IAEA has no enforcement authority. It was the UN Inspectors office and not the IAEA that found out Iraq’s nuclear development program in the 1990’s.
2. The 1970 NPT is falling apart. There is no longer a meaningful nuclear proliferation deterrence.
3. India and Pakistan exploded nuclear weapons in the 1990’s - nothing happened.
4. Korea exploded nuclear weapons in the 2010’s - nothing happened.
5. Iran has had a military nuclear program in place for decades - contrary to what the IAEA had reported about Iran for decades.