Actually, the first game to be played overseas is happening next year. It was a pretty big deal when it went down.

It IS a World Championship. Point is, there are European Football leagues, Canadian Football leagues, etc., however, people only play there with the hopes of making it to the NFL. The best players in the WORLD play in the NFL, and it's the highest benchmark one can attain when trying to excel at the sport of American Football.

It's not exactly an International sport based on popularity, however, it is recognized as a World Championship. Here is the article on ESPN.com that talks about the overseas games:

http://sports.espn.go.com/nfl/news/story?id=2637594