This is because "the country" is really an empire, not a country. Would you find it odd that people in places under the US's imperial control (either formally or informally) don't always speak English?
I don't know if it counts but the Philippines. -It used to be under US control formally if for only a little while, informally a long time.
They have the same problem China does and it's a smaller area, The most spoken language is Tagalog and even then
so many distance regional differences many can't talk to each other.
That's the way it was when I lived there; hitting the wikipedia it's much worse than I thought, as Tagalog has been replaced
with Filipino and English
Filipino is constitutionally designated as the national language of the Philippines and, along with English, one of two official languages.