This bill, titled the "Keeping China Off the Rails Act" , amends section 20171 of title 49, United States Code, to revise the application of manufacturing and content requirements for railroad freight cars. It specifically alters the definition of which freight cars are subject to these federal standards, moving from a single manufacturing date to a more dynamic, phased system. The legislation introduces a gradual implementation schedule over four years. For instance, in the first year, cars produced within the prior two years must comply, expanding to cars produced within the prior five, ten, and fifteen years in subsequent annual periods. Ultimately, four years after enactment, all railroad freight cars operating on the U.S. general railroad system will be required to meet the specified manufacturing and content requirements.