What documents do I need to apply for to successfully immigrate to the United States and return to China?

Immigration to the United States is divided into two stages, one is green card and the other is naturalization.

At the stage of your green card, you are still a citizen of China, and you don't need a visa to return to China.

If you are naturalized in the United States, you are an American citizen and need a visa to return to China.

Of course, no one forces you to be naturalized in the United States, but generally speaking, naturalization would be a more reasonable choice.