Name one international race won by an american car. It isn't possible because it hasn't happened on a track with corners other than banked left handers!
Le Mans - Never
Monza - Never
Monaco - Never
Silverstone - Never
Spa - Never
Magny Cours - Never
Corvette C6 ZR1- Le Mans GTEPro class win
Viper GTS-R= "won class at the 24 Hours of Le Mans, won the GT world title, won the 2000 Rolex 24 Hours at Daytona overall, and went on to win every race in the ALMS championship to take that title in its final racing season".
Class wins are a good place to start. Took a european to achieve it though! Overall in a decade or two?