I think you are construing bitcoin as a currency, which is in fact, not a currency but only as an alternative means of payment. No country or state uses bitcoin as their main medium of exchange in their transactions. Not to mention, there are countries that deny and prohibit the utilization of such, which is why it is wrong to view them as currencies being used in the world.

Lastly, bitcoin cannot be a currency with only a supply of 21 million in the world. This would make the currency very inflationary once it reaches the end of its supply in years to come.