Technically, the US has been using the metric system since 1893

Usually 13mm and 1/2" sockets and wrenches are completely interchangeable. But it depends on how many points in your sockets, I guess… I actually have one set of wrenches that are marked in both metric and SAE (as well as full sets of both, down to 64ths and half-millimeters in the ignition wrenchs).