As expected, american football is most popular in North America, which is where the sport originated. Specifically, the U.S. and Canada have the most football fans in the world by far. However, each year the game is garnering more and more popularity worldwide. Mexico, England, Japan, and Australia are among some of the countries learning to love the sport of football and developing leagues of their own. While american football is outshined by soccer in most of the world, fans the U.S. have consistently voted football to be their favorite sport since the 1970's.
So, while football's popularity is still predominantly in North America, the game has been making its way across the globe with leagues and fan bases being developed all over the world. The United States will always lead in terms of football's overall popularity for the near future. However, as football continues to grow worldwide, it wouldn't be surprising to see even more countries become passionate football fans as well.