Well, except the number of English speakers outside the US is much larger than inside the US (as per the wikipedia page you point to) by 5 to 1. Granted many folks are speaking it as their 2nd (or nth) language. But when you take into account the limited set of languages supported by ChatGPT one could reasonably assume English-speaking (typing) users of ChatGPT are from outside the U.S. as non-U.S. folks are in the majority of 'folks for whom english would be their first option when interacting with ChatGPT'. Even if you only count India, Nigeria and Pakistan.

Though of course OpenAI can tell (frequently, roughly) where folks are coming from geographically and could (does?) take that into account.