I'm not sure that's going to happen anytime soon. That would take away any power and freedom, each country holds. From my understanding though. One day, they will try to combine Canada, US and Mexico currency.
I've read in the NYT they truly would fancy digital currency......better tracking of EVERYONES money. No more working under that table or hiding funds. The problem....there's no way they will be able to stop digital/cyber currency theft. Too many viruses, theft, fraud...etc....
Durning the Bush administration....they pushed through a new act... called the Real ID act......Drivers Licenses with ALL our personal information coded in the digital strip....however, it's still being debated.....and for good reason...their excuse....better homland securtiy.....but in truth....more control of the US masses.....