English is a completely different language from American and yet the language American is also called English. Which must be a little confusing for people whose first language is neither of these.
American really is 'English as a Foreign Language' in a sense.
Sometimes the distinction is drawn by referring to American-English or Australian-English or British-English. I've never actually heard anyone refer to Geordie-English or Scouse-English and I bet you'd never hear anyone talking about Scottish-English either.
So, we all use completely different languages and call them by the same name.