Do foreigners belong to China after they immigrate to China?

"Immigrating to a country" does not mean that you must join the nationality of that country. Generally speaking, immigrating to a country means obtaining the long-term residency in that country (such as obtaining a "green card"), but if you want to join that country, you need to apply separately, meet the relevant conditions, and obtain naturalization approval. Only by joining the nationality of that country will you be recognized as a national of that country by law.

Therefore, if a foreigner "immigrates" to China, if he only gets a green card in China (China now has a "green card" system, but only a small part is issued), then he is not from China; If he is naturalized in China, he is legally from China.