system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What would happen if every country in the world suddenly started using the same currency?
gpt
It depends. If it goes off the USD then this would give Americans massive amounts of power as they would dictate the monetary policy and can print off new money for itself for the most part at the expense of everyone else. Whereas current when they print off new money they harm themselves for the most part. So the government tends to print as little as possible new currency; generally speaking.

Meanwhile currently say Canada can do the same. They print off new money to fund itself as needed. 

If that changed. Canada now can't print money to cover off its mistakes and needs. They end up forcing themselves to take less risks and acting more fiscally conservative. Meanwhile the USD could print itself and harm the Canadians. 

So what would happen would be far more commonly there would be countries having economic failures that they can't just print off money and the USD value would drop far less than it has been historically.

Now if we posit a currency which doesn't have a central country of control; much like bitcoin or perhaps the Star Trek federation credit. The problem is that inflexiblity of the currency is a lost tool that for the most part that isn't beneficial to society.