OK, what we have here is failure to understand what exactly the United Nations IS. It isn’t a government. It has no actual powers, other than what the member states agree to do. And why is that?
Because it wasn’t created as a transnational government (like the European Union), it was created as a way for already existing member states to resolve disputes short of war, so we could avoid World War III. Would the USSR in 1945 have joined any organization that interfered with the internal workings of the USSR? No, of course not. AND NEITHER WOULD ANY COUNTRY ANYWHERE IN THE WORLD.
Except of course, countries that have mutually beneficial relations. And this is how the European Union came about. But note that the European Union is of an entirely different character than the United Nations. The United Nations includes every state on Earth. It includes totalitarian dictatorships, monarchies, theocracies, and liberal democracies. Why would anyone living in a liberal democracy agree to let the government of a totalitarian dictatorship interfere with their internal workings?
I can imagine the United States becoming part of a transnational global governing body, but such a governing body has to be composed solely of liberal democratic states, such as those that comprise the European Union. Note the stringent requirements before any state can petition to be allowed to join the EU. Only liberal democracies of good character can be considered. Anything else is insanity, it would be like inviting the Soviet Union to join NATO. NATO was an organization set up for mutual defense against the Soviet Union, allowing the Soviet Union to join would have made NATO pointless.
The United Nations is a talking shop to allow existing governments of all sorts, whether fascist dictatorships or liberal democracies, to sit down and try to hash out differences as an alternative to war.
If you want a transnational government, you have to start with a brand new organization. Or, if you want to turn the UN into an effective transnational government, the dictatorships and illiberal states will have no place in the UN, and will either leave, or have to be kicked out. And then you’ll probably want to set up some sort of organization where the states, even illiberal states, can try to resolve disputes between themselves. And since the United Nations no longer serves that purpose, you’ll have to create a new one.
So wouldn’t it make more sense to leave the United Nations as it is, a talking shop open to any state of any character, and set up a new transnational governing organization? Or persuade the European Union to change its name to the Liberal State Union, and allow Canada, Australia, Japan, Costa Rica, and any other other interested liberal democratic states around the world, to join?