German fitness coach Shad Forsythe, is he the first American to win a World Cup? Have there been Americans on previous World Cup winning coaching staffs? I can't think of any.
No others, though there have been American coaches for other World Cup teams. The closest to winning was Afshin Ghotbi, who was an assistant coach for semifinalist South Korea in 2002. Other American coaches at the World Cup: Alketas Panagoulias, head coach for Greece in 1994; Dan Gaspar, goalkeeper coach for Portugal in 2010 and Iran in 2014; and Omid Namazi, assistant coach for Iran in 2014.