— -- The NFL's International Series shifts to Mexico City this week, and coverage will focus on the enormous support from local fans. Estadio Azteca will be sold out on Monday night as the? Houston Texans and Oakland Raiders?face off, a confirmation of the continued interest in American football outside United States borders. Less visible, but no less interesting, is the rise in player participation around the globe. A new adult league debuted in Mexico City this spring, joining dozens of semi-professional and club-level leagues in every corner of the planet -- from Europe to Asia to Australia.
The worldwide action is tracked daily by American Football International (AFI), a website and advocacy group run by Roger Kelly and John McKeon. Kelly is a former Canadian Football League executive, now living in Sweden. McKeon, a former player in a French league, is based in New York.
ESPN.com teamed with AFI to assess the quality and scope of Planet Football. What follows is a subjective ranking of the top countries from a standpoint of participation and local interest.