[Edited to make it more understandable question]
What if all nation use only a one currency or one global currency?, What will happen to our world?, What is the effect of every nation's or every country economy?, It can make people's unite each other?Any opinion.

If we are using one currency only then I think that we are susceptible to destabilizig economies as one variance change then all of is in the world would be affected. ALso it would mean that dime of the prices of items we are used to biging would not he the same.