What would happen with the economy if a global currency or a type of fixed change existed?

Question

What would happen with the economy if a global currency or a type of fixed change existed? ¿consequences?¿advantages?

Answer 1

It will never happen because many national governments do not want to give up the power of being able to print their own money.
If there was a global currency, who would control the printing press?
In the case of the Euro, it works only because each member country is required to limit the amount of debt they can carry and keep inflation in very specific limits.

Answer 2

global economy would fall apart