Recently a parent asked me whther it was correct to say “I’m a Chinese.”
Had to think about it for a minute, but said that it was.
I hesitated because to me at least it sounds odd. English generally uses the same word for noun and adjective when talking about nationality- “I’m Canadian; I’m a Canadian”, but there are exceptions; mostly European countries that have different forms:
These seem to me to be dropping out of use (with the exception of Pole?)
“He’s British” (or even “He’s a British guy”) would generally be used in peference to “Briton”.
For Chinese, though, I think the answer is different, at least in part, and the culprit is - you guessed it- racism.
Originally the noun for someone Chinese was “Chinaman” ; when this became identified with racist abuse, it was dropped- but the replacement is still awkward.
Maybe the same for Japanese- “Jap”?