What nationality is Lei Qian, the grandson of Qian Xuesen?

Lei Qian, the grandson of Qian Xuesen, is now an American citizen. Lei Qian's father, Qian Jinping, is the second son of Qian Xuesen. He immigrated to the United States with Lei Qian's mother on 1955. Lei Qian grew up and received education in the United States, where he received a doctorate and engaged in scientific research. Lei Qian himself once said that he was a patriotic China native, but he thought that his career and life were in the United States, so he chose to become an American citizen.