And I also think that the reasons why Countries adopt bitcoin and failure, though I have mentioned it but let me give the indept. Probably the total number of bitcoins in the space is not enough for them to accumulate and use it as a Fiat currency for all.
One thing everybody just need to understand is that Bitcoin can never take the place of fiat currency entirely, both works hand in hand, and thats why the value of Bitcoin is always represented in USD rate. Because the more a country adopts Bitcoin as a legal tender, the more the price of Bitcoin wil rise, because it's total supply is not enough, so in other to circulate round it has to increase in value. But if all the countries adopt Btc, its value will die drastically as there will be no competitive economy