The 30s, no doubt.
Back when none of the movies had any "messages", but were still played by cute actresses and handsome-ish actors.
Best movie of all times: Gone with The Wind.
Edited to add, NH###: to make you feel better, the Germans _did_ use quite a number of American and other tanks. French, Russian, British, whatever held still long enough got a swastika painted on the sides, and a big one on the turret to be safe from the Luftwaffe.