Could you see a future wherein the entire world shares one global currency, be it fiat or crypto? If I think it in a scifi kind of way, it would most probably be some digital currency that could all just use. It doesn't even have to be in this century. Maybe the next?
This could be difficult to control when we have different culture and economy every country as the standard is not the same. Policies every country had different and this can bring chaos and misunderstanding in every people. Maybe this could be possible if we have only one leader to decide for the whole world.
of course it will cause chaos, I can't imagine if the world only has 1 currency, how to distribute to many countries, how the economy is described in a country (because there is no local currency), and who will control the circulation of this currency (if only one currency)..