The first countries to use Bitcoin are a bit difficult to pinpoint definitively, as the cryptocurrency's early days were marked by a lot of anonymity and underground activity. However, based on available data and historical accounts, El Salvador on Tuesday became the first country to use bitcoin as legal tender, alongside the US dollar. So in this article I will highlight some of the countries that were among the first to embrace Bitcoin:

Norway (2009): Norway is often cited as one of the first countries to have Bitcoin users, with reports of early adopters as early as 2009. This is likely due to the country's high internet penetration and tech-savvy population.
United States (2009): The United States was another early adopter of Bitcoin, with the first recorded transaction taking place in May 2009. The US has since become a major hub for Bitcoin trading and development.
Japan (2010): Japan was one of the first Asian countries to embrace Bitcoin, and it quickly became a popular payment method for online goods and services. In 2016, the Japanese government even recognized Bitcoin as a legal form of payment.
Canada (2010): Canada was another early adopter of Bitcoin, and it has since become a popular destination for cryptocurrency startups. The Canadian government has taken a relatively relaxed approach to Bitcoin regulation, which has helped to make the country a friendly environment for the cryptocurrency.

It's important to note that this is not an exhaustive list, and there were likely many other countries that had early Bitcoin users. Additionally, the definition of "using Bitcoin" can be somewhat subjective. Some people may have simply been holding Bitcoin as an investment, while others may have been using it to make actual purchases.

Also there is some other factors that contributed to the early adoption of Bitcoin in these countries:

Tech-savvy populations: These countries all have relatively high rates of internet penetration and technology adoption, which made it easier for people to learn about and use Bitcoin.
Open economies: These countries have relatively open economies and financial systems, which made it easier for people to buy and sell Bitcoin.
Interest in alternative currencies: There was a growing interest in alternative currencies in these countries, due to concerns about government overspending and inflation.

Finally, Bitcoin has come a long way since its early days, and it is now used by people all over the world. However, the countries listed above still play a significant role in the Bitcoin ecosystem, and they continue to be at the forefront of innovation in the cryptocurrency space.