The only connection that I can imagine between Nazi Germany and the American left would be the marriage of convenience during the two years of the Molotov-Ribbentrop Pact, and that would only be the Communist Party left. The American fan club of the Nazis was the German American Bund, not exactly a bunch of flaming liberals. Other than in certain ethnic neighborhoods of New York and Chicago the Bund didn’t amount to much.
I wonder if anyone bothers to read William L Shirer’s classic history of Nazi Germany, “The Rise and Fall of the Third Reich” anymore. The first two chapters give a decent history of the origins of Nazism, much of it taken from Hitler himself. Somehow Adolph failed to duly credit any American political connections, but what would he know.
Nazism was pretty much sui generis, a point that Dennis Prager also likes to make. It had no connections to the American right or left, other than invented ones that people pretend to find.
Prager, “Learning the Wrong Lessons from Nazism”:
https://www.nationalreview.com/2013/12/learning-wrong-lessons-nazism-dennis-prager/