This isn't necessarily true. I recently met someone from Brazil who used the word "soccer" when speaking English. As an American living in Europe who's met people from all over the world, I've noticed that it's actually quite common for people to do that if the English they've been exposed to most is American English, especially if that was the dialect they were formally taught. In the case of Brazil, I'm pretty sure that American English is what would be taught in most schools.
As a German the game is Fußball (literally: football), but I just regularly say soccer in english because I cannot be bothered into finding out what the people I converse with think that football is and soccer is understood by everyone to be association football, i.e. the sport where the only hand that can be used is t̶h̶e̶ ̶h̶a̶n̶d̶ ̶o̶f̶ ̶m̶a̶r̶a̶d̶o̶n̶a̶ the hand of god.
Don’t you find that leads to unnecessary confusion? I use football if I’m out of the US, but in the US I’ve only heard people say soccer unless they’re being pretentious or recently moved here/on holiday.
I myself end up using soccer at times due to reflex, a mixture of learning american english and never reading/talking about american football hence barely seeing the word football being used, given the vast majority of english speaking media is US-based. It's not as uncommon as it may initially seem.