This story left some important things out. He and his family probably went to US to visit relatives of his wife. He decided to stay in America because he was not happy with his life in China.
How did he get his green card? There is only one way that is political asylum. It is ironic for a hero from China to apply for political asylum in US.
Anybody from China can apply for political asylum with the help of a crooked lawyer from Chinatown. We will never know what reason he used to apply for political asylum.