As of my last update, no country officially uses Bitcoin as its national currency. However, some countries like El Salvador have adopted it as legal tender alongside the US dollar. Other countries are exploring or experimenting with cryptocurrencies, but none have fully integrated Bitcoin into their official financial systems.
Several countries have significant Bitcoin adoption and usage, though it's not officially part of their national financial systems. Countries like the United States, China, Russia, Nigeria, and Venezuela have notable Bitcoin usage, either for investment, trading, or as a means of remittance. Japan and South Korea are also prominent in the cryptocurrency market. These countries have a large number of users, active trading platforms, and regulatory frameworks (or lack thereof) that contribute to Bitcoin's usage.