Definatly Eddie Merkx. He won every Sping Classic at least once, the Tour de France 5 times, Giro d'Itlia 5 times, the Vuleta a Espana twice, and two World Championships. Last year he raced the cycling leg of a triathlon in Isreal, and did very well. He still trains with his son's team, Lotto-Diavitimen, and runs a high bike factory.
As for your American King, Chris Horner? Lance Armstrong? Greg Lemond? Davis Phinny? Andy Hampsten? Major Taylor?