Redditor reddripper put together this excellent map of what "the beautiful game" is called around the world.
It's based on language etymologies. All the pink countries call it "football," or some literal translation of "football." All the blue countries call it "soccer," or some translation of "soccer." All the green countries call it something else entirely.
The takeaway: Americans aren't the only ones who don't call it "football." Not by a long shot. Much of Southeast Asia, Japan, Korea, Oceania, South Africa and even Italy call it something other than "football."
Check it out (via r/soccer):
The reason people all over the world call it football is simple — you kick the ball with your foot.
But why do so many people call it soccer?
Brian Phillips wrote a nice explanation for where the word "soccer" came from for Slate in 2010:
"It's an abbreviation of association football. Both soccer and American football come from the same set of precursor sports, which became popular in upper-class English schools in the early 19th century and spread across the Atlantic. All these games involved advancing a ball through an opponent's territory and scoring at the far end, but the rules varied from place to place. Ultimately, the version adopted as standard in the United Kingdom came to be known as association football, while another set of rules won out in the United States. Thus the Americans took to calling their gridiron variety football, and referred to the British sport by the slang term soccer, derived from the soc in association."