Keep Americans Safe Act This bill amends the federal criminal code to make it a crime to knowingly import, sell, manufacture, transfer, or possess a large capacity ammunition feeding device (LCAFD). The bill does not prohibit, with respect to an LCAFD: importation, sale, manufacture, transfer, or possession related to certain law enforcement efforts, or authorized tests or experiments; importation, sale, transfer, or possession related to securing nuclear materials; and possession by a retired law enforcement officer. The bill permits continued possession of, but prohibits sale or transfer of, a grandfathered LCAFD. Newly manufactured LCAFDs must display serial number identification and the date of manufacture. The bill also amends the Omnibus Crime Control and Safe Streets Act of 1968 to allow a state or local government to use Edward Byrne Memorial Justice Assistance Grant Program funds to compensate individuals who surrender an LCAFD under a buy-back program.