I feel its america.also china but they still trying to solve the bitcoin banned issue to thier country.
Yup you are right the America is now showing the great interest in the bitcoin at this time because all the people are having the bitcoin fun and the value of the bitcoin is now increasing more an more I can see the positive growth of the bitcoin for the very slow price and the valuable income of the bitcoin I know the fast growth of the bitcoin will give you the real value and this is the reason why the bitcoin is increasing.
In my opinion the country with wide use of bitcoin is Vietnam because Vietnam is the country who started accepting and using bitcoin as their regular and legal currency first and there are ATM machines for withdrawal bitcoins and the people use their bitcoin as paper currency in their local markets. South Africa and India also started using bitcoin but I think that Vietnam is number one in using bitcoins.