It was always a stone cold lie created by left wing authoritarians from the Frankfurt School during the McCarthy era— that Hitler was was a rightist.
Americans from the 1020s-1940 understood the nazis another german left wing street gang—like the communists in the 1920’s— that came to power.
Nazis and Communists were fighting in the streets. When the Nazis came to power they banned and imprisoned the Communists and Socialists and made alliances with the Nationalists and the military. However we think of the Nazis now, people at the time considered them to be right-wing, based on what they saw going on.