Let me offer a slightly different take. I view the 1930s -- aka "the Red Decade" -- as the breaking of an Old World tidal wave on the American shore. Iow, it was new and alien to us rather than (or far more than) an expression of the totalitarian undercurrent you refer to. It was the arrival of the French revolution supplanting our own libertarian beginnings.
We like to point our fingers at the nasty statists in Italy, Germany and Russia. Albert Jay Nock pointed out -- contemporaneously -- that the same statist philosophy prevailed in England, in France, and was very much at work here, in the New Deal. (Survivors of the New Deal era still think FDR sits next to, and slightly above, God.) It was all the same stuff.
Now, there is nothing like internecine warfare for bloodletting! The differences were miniscule, but the socialist brothers -- red, brown, black shirts -- fought it out furiously for their particular doctrines. From the old American libertarian view, there's not two cents worth of difference in the bunch. Hitler's standing in the club is just as authentic as Mao's or Lenin's. Mussolini wrote purer expressions of statist belief than any of them.
We remember that they fought on the streets of Berlin. We forget that they fought on the streets of New York -- in uniform! All those Nazi and Fascist rallies and Communist May Day marches in Europe -- we had them here, in uniform. I remember coming across a column by Walter Lippmann, the liberal's liberal, treating Hitler with utmost respect. FDR's NRA, the old Blue Eagle, was expressly modeled on Mussolini fascism. Yes, of course there was strong support here for the Axis.
From the nativist view, again, they were all the same critters. They thought so too, in their fashion! In the street wars here as well as in Europe, the Red shirts and the Brown shirts were each other's best recruits. And look at the two years of the Nazi-Soviet non-aggression pact when Hitler and Uncle Joe were buddies! They all had the totalitarian frame of mind. Of course that kind of thinking is still around, big time.
Amazing how WWII blinded us. We entered the war (and remained) aligned with the Reds. Opinion was shaped accordingly against the Blacks and the Browns. But it was much more a brothers' war than we are yet willing to admit.
All this ranting and I'm not even on my third cup of coffee :-) Take with the usual dose of salt.