Well that is not strictly true. At the time, Bentley, Bugatti, and Alfa Romeo were kicking ass on the track. Duesenberg, Pierce Arrow, Cadillac, Peerless were all comparable American luxury cars ...as were European marques like Dalahaye, Hispano-Suiza, Voisin, Isotta-Fraschini, Rolls-Royce, Daimler, Lancia ...there were many great car makers in the 1930s, the Germans were not the only ones producing amazing cars at that time.

BTW, look at this ridiculous Hispano-Suiza limousine from 1923.