American football has first dibs on the bulk of the talent pool in the US. Its not like some kid in France or Latvia is likely to start playing at 16 and find their way into the NFL. Not impossible but very unlikely. This makes the point you thought you were making about the 3% somewhat inconsequential.
The most populated country thats a soccer/football power is what? Brazil maybe? China's not a soccer/football power and the US isnt a football power. Those are two countries with very large populations that arent as dedicated tp soccer/football as much as many smaller countries. But its kind of comicsl to see people crow about soccer/football being more global in reference to American football because of a few large countries (population wise) then 40 countries the size of Latvia. Nice effort though.
To add:
Depending on your source, the 5 most populated countries in the world are as follows:
1. China
2. India
3. U.S.
4. Indonesia
5. Pakistan
Nigeria is 6. They're mostly competitive. Brazil is 7. Its the most populated country that one might legitimately consider a soccer/football power. Soccer/football is global when the five largest countries in the world an at least 3.5 million in population is standing on the sidines?