yes it’s true that modern English came basically from England. And 99.9% of the time Americans and English (people from England) completely understand each other as well as countries where England set up the education system like in India. But English can be a very dynamic language, and the regional dialects and slang can be so strong that even people within America might seem like they are speaking totally different languages. But all languages have this – language is often split not just geographically but socio-economically and is used as a way to identify yourself to others as being from the same ‘area’ or ‘culture’ – and also used to label people by people in higher socio-economic classes. I remember reading somewhere that certain prep schools for the very rich would create specific ways of saying things or even have terms that behave as a ‘signature’ in an actual secretive fashion just to be able to identify each other and more importantly – identify who ISN’T a ‘member’. but i don’t think it’s as extreme as – for example – when Latin split into French, Spanish and Italian after Rome fell. Those are very different languages. I understand non-native English speakers almost 100% (usually) and English changes constantly. it’s a living languages. English is more about convention (how people use it) rather than rules about how it should work. The “rules” are so convoluted and sometimes contradictory, that it’s more about what people just agree to for the moment or some movement in technology changes the popular usage of a term (computer means very different than what it used to mean: used to mean a person who computed numbers). Think about how you would explain the work ‘yo’ to a new English learner. Or how Facebook has changed the way we use verbs such as ‘like’. It’s used as a noun regularly now – “how many ‘likes’ does this person have?” that made no sense just a couple years ago. now we can something like ‘i find myself re-tweeting more than liking thingsi find online…’ imagine saying that to someone just 5 years ago.