Now Bitcoin can't serve as a medium of exchange in some small towns, but there are many places where it's accepted. That proves Bitcoin has a big potential to become "real money".
But Bitcoin is still more widely used as medium of exchange than any Fiat currency out there. every country has it's specific currency and that can only be used in that specific country. US dollar is a currency which can be used as medium of exchange in some other countries but not in all. and Bitcoin is used as medium of exchange in even more countries than US dollar. you can use Bitcoin in Us and China equally without any problem.