I actually don't think there would be all that much Genghis Marker in the US; immigration to the US from the former Mongol Empire has been pretty limited.
You'd probably find a bit of it in some people of Russian and Eastern European descent in this country.
Oops, I forgot about all the Persians that came here after the Iranian revolution. They'd probably have some of the marker. Biggest concentration I know of is in Northern Virginia.