The passion in the US for college football is frankly astounding. Most of us other-worlders attend university for the education. But then Oxford and Cambridge aren’t colleges. Just like students don’t go to Harvard or Yale for their football program. An Oxbridge sporting blue is typically given for a student who has earned international selection. If you have “merely” played for Oxford against Cambridge (or vice versa) then you have earnt a half-blue.
A note to the OP, which I’m sure would not be ground breaking news:
If you want to know “Why has gridiron football never gained popularity outside North America” you aren’t going to get the answer from North Americans.
Explicit case in point:
Which is indolent and utter frog shit.
In pre-COVID times 1 in 8 people in Melbourne either played or attended an Australian Rules game every weekend. We spread our sporting interests a fair bit thinner. In Sydney we aren’t so sportingly fanatic. But in the year pre COVID I played, umpired or attended games of AFL, Rugby League, Rugby Union, soccer, hockey, cricket and tennis. In season I watch a game of baseball and ice hockey on streaming service most weeks, bit less for basketball. Watching Olympics/Paralympics in lockdown was simply soothing for the soul. I enjoy the occasional NFL documentary etc but I don’t warm to the sport. Mind you, I don’t warm to ten-pin bowling either.
NFL is a game you watch. Revel in all those “high value commercials” as a US sporting patriot once expressed it on the Dope. “NFL is best viewed through the froth of a Budweiser”, as a less reverent American colleague put it. It’s not a game for the players. The spectators want to be the coach. Move the living chess pieces. Be the guy who calls the play and have all the guys on the pitch follow their instructions. Do precisely as you are told or you are off the team. Make a mistake, you are off the team. If it’s not going to plan you can just kill off the play and start again. It’s a video game in real life.
I can only speak myself but generally the non-NFL side of the world want to play the game. They want to be on the pitch. They want to have a role in the game . I want to play on both sides of the field. Play attack and defense. Score goals. Save goals. React to changing circumstances of the game. Be challenged. NFL doesn’t tick any box for me.