Give UN Sovereignty
In the United States, we had a system called the Articles of Confederation. It was the first system to govern the thirteen former colonies, and it was famously ineffective. The central government could make laws, but not enforce them, and each state acted as an independent country. Then the Constitutional Convention amended the Articles of Confederation into the modern United States Constitution, the model for the constitutions of most modern democracies. The states had to give up some of their powers, but the new federal government provided unity, stability, and was able to push and enforce a lot of important ideas from the top-down that might not have otherwise penetrated some states (think Civil Rights in Alabama).
The UN is a good idea, though it could definitely use a post-Cold-War makeover, but it suffers from the same shortcoming as the Articles of Confederation. It can pass resolutions but not enforce them. Nations can sign on to treaties on human rights and then violate them with practically no consequences.
We're all in this together, and we need to start acting like it. We need to transcend our petty, local viewpoints and do what's best for the world. That means surrendering some national sovereignty to an international federation of some kind, and the UN is in the best position to take on that role.