Is immigrating to the United States the same as changing American citizenship?

Generally speaking, immigrating to the United States means getting an American green card. You are still from China, and your green card is equivalent to your temporary residence permit in the United States. You are just a China citizen who can live permanently in the United States, not an American citizen. The U.S. government doesn't consider you an American citizen. You can't apply for American citizenship until you get a green card for three years, and you need to pass the American naturalization exam. If you change your nationality, you will be a foreigner and have nothing to do with China. At present, China people who emigrate overseas generally only get green cards and do not change their nationality for the convenience of returning to China.