Theodore Roosevelt was a true proto-fascist, and it is my personal opinion that had he lived to see Mussolini's movement he would have been the first American Fascist with a capital "f." His youth, his crusading nature, his dramatic speaking style, his lauding of "the strenuous life," his jingoism, his militarism, and his domestic interventionism in the economy all point in this direction.
There was a "progressive" element to the temperance/prohibition movement (especially in the early years), but by the Twenties the Fundamentalist Protestant element had become just as important, if not more so. The "wet" states and populations were in the areas we now recognize as liberal, while the Bible Belt was solidly "dry." Also, I notice that Prohibition gets lambasted by the liberal media quite often (because it "didn't work"), yet that same media wants to apply the same logic to guns. Furthermore, conservatives' arch-villain FDR made the repeal of Prohibition one of his major issues.
I believe the author makes an error when he identifies Woodrow Wilson's "goon squad" as "the American Legion." The American Legion was not organized until 1919, and it was made up of the American Expeditionary Forces. I believe I've read about the organization the author truly has in mind, and it isn't The American Legion.
Lay off of Julia Ward Howe! The Battle Hymn of the Republic is one of the most inspirational patriotic songs of all time! And if the Union's confidence in the rightness of its cause is "fascist," isn't every government at war for what it feels is a "just cause" similarly "fascist" (including the Confederacy, which fired the first shot)? Seems to me this is one of those universal human attitudes shared by fascists rather than a specifically fascist attitude. (Pinging wideawake for the Julia Ward Howe thing.)
I think the notable distinction between the ideals of a non-fascist society and the ideals of a fascist society are - as Mussolini emphasized and as Carl Schmitt analyzed - that the fascist society is built on a mythic goal.
And by "mythic" neither Mussolini or Schmitt meant "imaginary" but that the goal was invented by the fascist movement, invested with religious significance and raised to a transformative event.
To the Nazis, the elimination of Jews from the world was a way to save Aryan man from destruction and to usher in a glorious new age of Aryan world ascendancy.
The Holocaust was not imaginary, but its ideology and its contemplated results were mythic.
The Battle Hymn Of The Republic is not really in that mold.
It basically says, in florid language, that slavery is a blemish on a land that considers itself a land of freedom and that fighting to end slavery is moral and that God is happy with and supports those who fight to free their fellow man from oppression.
This is not the creation of heretofore unknown myth, but a repetition of common Scriptural tropes: that God is on the side of the just, that oppression of the poor and weak is something God hates, and that those who fight to accomplish God's justice will be rewarded. Her imagery is that of the Second Coming, in which a glorious Christ will judge the nations - and the message is that if the USA fights to end the oppression of slaves, then it can feel confident of that judgment when it comes.
If The Battle Hymn Of The Republic was about killing every last Confederate without mercy and said that the ending of slavery would create an earthly paradise in which the USA would conquer and rule the whole world, then it might be characterized as fascist.
But it doesn't really fit the mold.