system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Would a centralized currency throughout the world work well, if at all?
gpt
One problem with a world-wide currency is neatly demonstrated by Greece and the Euro.

One major way that a country can deal with hard times is to allow, or even force, their currency to be worth less. That makes the things you, as a country, make cheaper, and things you buy from other countries more expensive. So the country loses less money paying for exports, and makes more money selling its now cheaper exports. They can also create new money to pay for government spending, creating employment and pulling the country back onto its feet.

If there is only one currency, a country can't do this. Their citizens keep buying imports, and their exports remain too expensive, and they can't recover without cutting back hard on government spending, which makes the hard times worse.