I am sure there are countries in which Soccer is not played in an organized league fashion. All I need to point out is one, and then there can be no world cup (following your line of thinking
The world cup will accept anyone who fields a team and wants to enter, aslong as their qualifications are satisfactory… just like the olympics. Just like Miss Universe. In fact, Miss Universe WOULD accept alien species, if we knew about them, I remember reading an article in time where that was discussed.
That said. North America isn’t the only place “American” football is played. The European league, though it has some different concepts and rules, is largely the american game, like the CFL, OR the XFL in it’s day.
Regardless, Like the MLB, even IF someone could field a team good enough to beat the socks off your run of the mill NFL team, they wouldn’t be allowed to challenge them. THUS the “World Champion” title, should be stripped from anyone who’s ever said they held it.