American football is not popular outside America

Historically, there’s no one real reason, but the creation of ‘football’ in the USA predates the creation of codified Association Football in England by at least 20 years. Whilst most of the world took to the association rules, based on the rules created at schools like Eton and Charterhouse, footballers in American colleges took the lead of their Canadian college comrades in preferring the Rugby school rules. The exact same thing happened (albeit much later) in Australia and New Zealand. From there, American and Canadian football devised their own rules, and independent of a rules committee - their game evolved into what it is today.
I still struggle to see why it bothers so many people that Association Football has never ‘caught on’ in the USA. I find it a miracle that Association Football has spread so far and so wide like it has, whilst other games, like Baseball, Cricket and Field Hockey, did not.