Certain beliefs about the United States once seemed unshakable in China: that America was hopelessly far ahead, for example, and that moving there guaranteed a better life. That’s no longer how people talk in Beijing, where I live, or on Chinese social media.These days, the chatter is more about the precarity of life in the United States. A term from gaming has gone viral on social media: Zhanshaxian, or the “kill line,” is the point at which only one more hit is needed to knock a player out. Americans allegedly live alongside it, buying on credit, carrying heavy debt, and…