The act of using one currency in the world mean's that every country in the world uses the same currency.
The use of a global currency will be the starting point of eliminating suffering in the world.
All nations would certainly benefit since there would no longer be currency risk in international trade. Traders would no longer fear for currency fluctuations.
Economically developing nations would also benefit base on the introduction of a stable currency, which would form a base for future economic development. For example, Zimbabwe suffered through one of the worst hyperinflation crises in history. The Zimbabwean dollar had to be replaced in April 2009 by foreign currencies, including the U.S. dollar.
It has gotten to a point in life where global currency is now needed in the world in other to end constant inflation and suffering in different countries.
When there is one generally accepted currency in the world, inflation and poverty will no longer be one country fight but a world fight.
As long as that one currency is controlled by a single entity, the sufferings won't end. Having a single currency controlled by a single entity, is not going to solve wealth distribution inequality issue. That won't solve why the poor are getting poorer and why the riches are getting richer. Unless that one currency is truly decentralized, there's no end to the sufferings.
No country is going to take responsibility of the poverty of another country. Europe tried to do that and UK stepped out saying they won't take the burden of debt of other countries. World is a cruel place. Countries like US, UK, China, Russia will always try to control the power they already own.