Pangur
Donor
Or perhaps it's because until recently Association Football was a minority sport in those English speaking countries
Date Leagues founded
England 1888
Scotland 1890
Canada 1912 (or 2018 - depends what you call a national league)
Eire 1921 (and it's normally called football not soccer)
Australia 1977
USA 1988
New Zealand 2005
The only corruption of language has come from the countries which already had a strong "football" sport, be it rugby, gaelic, Australian rules or American rules.
Besides - even if you add up the total population of the "soccer" playing countries they are no more than 5% of the world (and I bet most hispanics would refer to it as futbol not soccer)
But to get back to the OP - American Football is probably one of the few sports that is becoming less accessible, more complicated and higher cost of entry to casual players in its competition format not more. That is never going to work well for mass participation
Leagues, fair enough however I dispute your 5% is way of the mark Pretty much every nation has a crack at making the world cup and that game is played in most parts of the world even if its kids playing with a rolled up rag and piles of stones to mark the goal mouths are