Technically (legally) the US has been Subject to the UN from day one of the UN (early 1940s). The Security Council has Ultimate Authority (legal Sovereignty) of the United States and all other countries who signed the UN (which is pretty much all). As just one example of the enumerated powers of the Treaty that we call the UN, they have conscription powers of almost every single person on the planet, including all people of the US, whenever the fuck they want. Most people don't realize that, since that has never happened in the US, but it has happened in some of the smaller countries on occasion.

These powers (and many more) were there from day one. This is how the UN was designed. It is absolutely the Sovereign of the World, and it has been for 80 years.

These new things that are happening are not "giving the UN Sovereignty," they already had it. These new things are just adding on specific enumerated powers so that people will see that the UN wants to have the powers they already have. In other words, these things are just for show. The powers are already there.

But what does it mean that the UN is "Sovereign"? Most people don't really understand what that means. And it is not straight forward, since it depends on which legal system you are looking at. Ultimately, Sovereignty is a function of Natural Law. By Natural Law every single Natural Person is Sovereign, and no one can be the Sovereign of another, whether they be other Natural Persons, or other incorporated entities (government e.g.).

But within any manmade legal system (and there are several in a semi-hierarchy), a Sovereign pretends to be the Ultimate Authority and enforces their pretense with coercion. You cannot be a Sovereign (other than yourself) by any other method. You can have a governor (which means, "to steer the ship,") by you cannot be a Sovereign, except by pretense and by force.

this is not how contracts work lol. Express, explicit consent is required

That's not really true. There is a scope in which it is true, but most of the really big contracts, the ones that really matter do not require explicit consent, but rather implicit consent. For example, the US Constitution, and the governmental corporation that it incorporates, is a Treaty, AKA a contract. I did not give my consent to enjoin that contract. On the contrary, I VERY MUCH do not want to be a part of that contract. I however do not have a choice. Well, there is always a choice, but I don't have an effective choice other than death, or being a part of a virtually identical contract with some other governmental corporation. I can't live in my home without being a part of the contract I didn't sign. Indeed, I can't even effectively live at all without being part of the contract I didn't sign. If were to try, the systems of force are so powerful, I would be squashed like an grasshopper in a crow convention.

Most people aren't even aware that they have enjoined the contract at all. They don't realize that they have given consent, thus it is implicit. And, as already stated, there is no exit clause.

Second, we can just withdraw from the UN all together

We can. It is just a Treaty. However, doing so will have consequences. There are always consequences. Because of the Treaty, breaking the contract would be an act of war. That could end poorly.

Frankly, I think the only way to effectively end our participation in the Treaty is for the entire population to understand the scam that we call the UN, and how it was created by Rockefeller/Rothschild to create their One World Government, under their control.