Is this film released in 2000 or 2001?

According to the release dates on IMDb, "Memento" was released in the fall of 2000 outside the USA, especially in the UK, and was released in the USA in March or May of 2001. Since this movie is American, even though it was directed by a British filmmaker, do you regard this as a 2000 or 2001 film? I'm just asking. I think I regard this as a 2001 film, since it's American.