Is sentence "I am a Chinese" correct?

I read from an article about this confusing sentence.

since Chinese is both adj and noun,I suppose "I am a Chinese" is grammatically correct just like "I am an American"?

Do native speakers prefer to use "I am Chinese"?

There are two issues here Grammar and Asian vs America

Personally I would go with the fact that Chinese is non countable so therefore no "a"

You are Chinese is the normal preference. Respectively I am sure that there are few Americans who refer to themselves as I am an American I am sure that the saying is I am American just the same as I am British.

"The Chinese" would be acceptable as a temporary definition if you were the only Chinese person in a group (provided you had no objection to being singled out).

There is a difference between.

"I am a Chinese"

and

"I am an American"

To compare you would probably have to say I am an Asian (not Chinese).

Although American is associated with the United states, so much so that it has become a normal association. The fact remains that North America is a continent and the United states of America is a country on that continent. Because there only 2 countries nominally associated with North America it has become generally accepted that Americans refer to citizens of the USA and Canadians are citizens of Canada. However, technically that is incorrect North, Central and South American populations are all Americans.

In fact the definition of American is: Cambridge English Dictionary American is: relating to the United States of America: or relating to North or South America

Therefore to say you are Asian is the counterpart to you are American.

American adjective

of or relating to the United States of America:

of or relating to North or South America