Wouldn’t a global fund for any disaster in the world also be a form of insurance that covers me? I would be happy that there’s a global fund for me if my country goes down the shitter.

By the time your country goes down the shitter the corrupt unaccountable bureaucrats who manage that global fund would have embezzled all the money.

Wouldn’t that apply to any kind of disaster or disablement fund? I don’t get it.

Smaller scale is better. It’s closer to the non-politician voters. The UN is many layers removed from me and I have no actual control over what they do or who works there, whereas I can write to and vote for the person who runs my neighbourhood, city, etc.

That's a reasonable take, but a far cry from "extortion".