Earlier quoted context omitted.
I’m not American and don’t live in America (I presume by “America” you mean the United States?), but shouldn’t it be “… refuse to improve their English”?
Presumably the parent comment meant that their English was poor to the point where they couldn’t communicate effectively with the worker, not that the worker was getting their point across but lacking pristine grammar. As an anecdote I’ve found that non-Americans from well off families tend to speak near grammatically perfect English because that’s how foreign languages are taught.
As an anecdote, an eternal rule for venting about insufficient language skills of damned foreigners on the Internet seems to be that it must be articulated by at least one demonstration of one's own inability to possess the very competence demanded (e.g., through absolutely careless spelling, grammatical error, etc.), which my contribution above was simply commenting on ironically— with a tangential spoof of U.S. exceptionalism of course.