They definitely didn't use Earth - it's a CGI shot, and I don't think you can actually see any continents, but I may be misremembering.

Or maybe one big Asia-sized continent and a smaller, Australia-sized one? Come to think of, world government could also explain the ubiquitous bilingual signage despite the total absence of any speakers of any other language. Maybe Haixing has two official languages, but the actual speakers are mostly clustered in two different areas/on different continents.