due to the efforts of powerful conservative elements in the US government

More like because the Democratic administration at the time was fond of fascism.

“The Fascist Principles are very similar to those we have been evolving here in America.” - Roosevelt's National Recovery Administration

"There seems to be no question that [Mussolini] is really interested in what we are doing and I am much interested and deeply impressed by what he has accomplished and by his evidenced honest purpose of restoring Italy." - FDR

"The Roosevelt administration envisages a federation of industry, labor and government after the fashion of the corporative [fascist] State as it exists in Italy.” - The New York Times

“It [fascism] is the cleanest, neatest, most efficiently operating piece of social machinery I’ve ever seen. It makes me envious. I find Italy doing many of the things which seem to me necessary … Mussolini certainly has the same people opposed to him as FDR has.” - FDR adviser Rexford Guy Tugwell