Sales of US cars is small because Ford and GM have european factories with product lines designed for european taste.
Only niche models are sold, like Corvettes, Camaros and Cadillacs. Prices are often much higher than in the US and are therefore less competitive against german premium brands.
Ford doesn´t sell any US model in Sweden.
Chrysler sell the Voyager and 300 as Lancias, only Jeep (Wrangler and Grand Cherokee)have the original name.
At least in Sweden, US cars have a better reputation than italian ones which are equalled with quality problems. This rebadging weakens Chryslers position in my opinion.

US cars haven´t sold in large numbers here since the 1960s, the Valiant was quite popular.
As the car industry as well as the society in general gets more international (Chryslar-Fiat,Renault-Nissan etc) I think it is unlikely that the genuine american car will return to its strong market position. US made products may come back but only as a part in a product line (say version of a model) or as parts (engine, transmission etc) in any car.