Have always wonder which currency would the world accept if only one currency was to be used. Maybe the dollar?, don't think so, The British won't tolerate that.
Cryptocurrency?. Maybe. Until the advent of cryptocurrency, I never thought that would be possible but it seems possible.
The world is not too far from a unified currency.
Honestly bitcoin got the capability but unfortunately it is slowly turning as a pure asset rather than being a payment processor/an alternate to fiats.