Basketball is pretty self evident for how it can translate easily, due to like Soccer it having a relatively low entry level for equipment needs. I was thinking though how a sport like Baseball the "American past-time" has very popular leagues as far off in Japan and South Korea.
A lot of that was established early on. So I guess the way to spread American football (call it "gridiron", or handegg, why not) is to have it be spread early. It reached Samoa in the 1960s, and nowadays, Samoans have a very noticeable presence in the NFL. I think if you could introduce American football pre-WWII to certain places, you might get some decent local play. Especially because older football had less equipment. If the locals enjoy the game, they'll surely adapt to the changing rules of equipment standards.
I think getting it baseball level popular is doable. It would be kinda cool if it became popular in Polynesian and other Pacific nations, going by the amount of Samoans in the sport. Even if competing with rugby in New Zealand is probably a no-go. Maybe in parts of Africa too, since there's a decent amount of ethnic sub-Saharan Africans who play gridiron who either immigrated to the US or have immigrant parents.
Oh, and the biggest thing, someone can actually build a team to defeat the United States national American football team in the "IFAF World Championship", which seems to attract nothing but laughs from the American media by how badly the US decimates all opponents. Seriously, a bunch of college football players who graduated and were undrafted by any league, not even all from Division I schools, destroy everyone, everytime, guaranteed, until they let someone win. If someone can beat that in a serious match, consistently, then maybe there's a hope for international American football. But I suppose with an earlier POD, that won't be necessary and the US might not be forced to play international games with both hands behind their back because there's actually some level of play. Maybe it's like the World Baseball Classic where the US never actually wins anything. Or it ends up like international basketball where the US team is utterly stacked and thus dominates the sport.
I don't know if it is equipment requirements as much as the game's intricate complexity compared to other codes. I was playing scratch games of AFL when I was 4 and played organised soccer at 8 years old, but can a handful of little kids play American football with the excruciating complexity?
When I grew up everyone knew the rules by heart, and organising a simple game was no problem once you cut out the complex parts. After all, touch football and flag football exist for a reason.