It’s known as fantasy football to anyone outside of North America.
Fantasy American football is extremely popular in the US, so I think a lot of people would automatically assume that's what was meant.
And yes, we're aware that people in different countries use different words for things.
(And no, actually, it's not called "football" everywhere outside North America. See: https://en.wikipedia.org/wiki/Names_for_association_football)
I have absolutely no problem with people calling it football, soccer, calcio, or anything else.
According to that one ~2/3 of HN visitors are not from the US. It’s old though, and now I’m wondering what the current statistics would look like.