"Teacher Li is Chinese."
中国 = China (country)
中国人 = Chinese (person)
Literally, it means "China person".
法国 = France
法国人 = French (person)
中国 "Zhōng Guó" Means "China"
人 "Rén" Means "People"
Therefore 中国人 "Zhōng Guó Rén" Means "China People/ Chinese People"
I could be wrong myself, but since that is the word for "person", it changes country name to nationality name.
人 indicates the sentence as a chinese person therefore they should change this.