Maybe in 100 years the NFL will be part of a global network of leagues, as seen in today's soccer.
The facts are that football remains very much an American only sport.
Even basketball has expanded beyond American borders.
Can you even name a non-American groomed all-time great player? I know there's a few Canadians, a German Sebastian Vollmer, & a Polish kicker name Sebastian Janikowski, but seriously there are very few, due to the limited number of leagues globally.
If the NFL was serious about growth they'd focus more on exporting their sport on a grassroots level. You cannot simply put a team in London, Tokyo, or Berlin and expect immediate success. Heck even the Bills latest foray into Canada has shown the lack of Canadian interest - Canada is a hockey first country.