I just found some American cars on mobile.de, which weren´t officially sold here:

US-Ford Focus
http://suchen.mobile.de/auto-inserat/ford-focus-2-0-16v-automatik-klima-orig-17000km-heidelberg/153384054.html?lang=de&pageNumber=2&__lp=19590&scopeId=C&sortOption.- sortBy=price.consumerGrossEuro&makeModelVariant1.searchInFreetext=false&makeModelVariant2.- searchInFreetext=false&makeModelVariant3.searchInFreetext=false&minPrice=5000&ambitCountry=- DE&negativeFeatures=EXPORT&categories=Limousine&categories=Van&doorCount=FOUR_OR- _FIVE

Nissan Altima:
http://suchen.mobile.de/auto-inserat/nissan-maxima-2-5-autom-hamburg/157902156.html?lang=de&pageNumber=3&__lp=19590&scopeId=C&sortOption.sor- tBy=price.consumerGrossEuro&makeModelVariant1.searchInFreetext=false&makeModelVariant2.- searchInFreetext=false&makeModelVariant3.searchInFreetext=false&minPrice=5000&ambitCountry=- DE&negativeFeatures=EXPORT&categories=Limousine&categories=Van&doorCount=FOUR_OR- _FIVE

And a Audi 5000:
http://suchen.mobile.de/auto-inserat/audi-100-5000-s-rarit%C3%A4t-gaimersheim/166211258.html?lang=de&pageNumber=18&__lp=19589&scopeId=C&sortOption.- sortBy=price.consumerGrossEuro&makeModelVariant1.searchInFreetext=false&makeModelVariant2.- searchInFreetext=false&makeModelVariant3.searchInFreetext=false&minPrice=5000&ambitCountry=- DE&negativeFeatures=EXPORT&categories=Limousine&categories=Van&doorCount=FOUR_OR- _FIVE