There is a scholar called Braj B. Kachru put up a three-circle model for us to understand the global spread of English:

The inner circle countries where English is the first and dominant language extensively used in extensively in both private and public places such as the United states, Britain, Canada, Australia and New Zealand.

The outer circle countries where English has a long history of institutionalized functions in education and governance domains such as  India, Nigeria, Pakistan, Singapore, Singapore, Sri Lanka, most of which were previously British or American colonies.

The expanding circle countries where English is often taught as a foreign language. These countries include China, Japan, Korea, and some European countries such as Hungry，Poland,etc.

The question is when English transports from one place to another, is the English the same as the English used in its birthplace? Of course not. It may contact with the local language and culture and develop into localized English varieties.

If the global landscape of English has already changed or been changing, what is the point we still stick to the so-called American English or British English while ignoring all other varieties?