Countries like El Salvador and not so recently The Central African Republic are Trail Blazers in the aforementioned.
While BTC was a legal tender in these two countries at one point in time, BTC is no longer a legal tender in the both of them. So i would not be wrong to say that there is no country where BTC is currently a legal tender. However, BTC is legal in so many countries and you can spend BTC freely if you find a merchant that is willing to accept it from you.
It does not matter if countries make BTC a legal tender, it does not limit its development. And to be honest, i cannot see the next country that would be willing to make BTC a legal tender.