It's not that Americans call it soccer, it's that they refuse to call it football, or even permit it to be called football, that's annoying. When I call it football, many Americans actually say to me "It's not football, it's soccer, football is ... (insert long boring description of American Football)" and I always reply "soccer is short for association football". It's not that people from the UK don't already know this, we do, the issue is that Americans don't know where the word soccer comes from.