My first thought was much the same. ..and yes I'd read that thread, thanks for the link. These two post contained some interesting points:
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One of the butterflies that would really concern me is the FBI. I'd think that Hoover probably gets to run wild(er) in chasing down anyone implicated, and trying to prevent another. You really could get something of a witch hunt, and it definitely won't be good for the military. I wonder if we might not see the US entering the war significantly weakened, having spent a good decade afraid of it's military. I can't imagine the state of the forces being nearly as bad as the Soviet, but you are very likely going to see a loss of talent and experience somewhat similar to what the purges caused.
J Edgar made much of his political traction as a anti Communist, but that may have been simply what his best 'customers' or patrons wanted. He might end up on the wrong side of this, but if he side steps implication then whatever 'files' he has may prove useful to the opponents of the B-plot, as would his well publicized G Men.
As for the military, there will be a clear split. My take is democrats (small 'd') like Beutler were the rule not the exception in the officer corps. Among the Lts, Captains, & Colonels there was a large portion of midwestern farm boys like Krueger or Ike, or frontier roughnecks like Dolittle with little sympathy for the elitist social ideas of those from the 'Right Families'.
Depends on how it shakes out, if the plot is foiled due to mid ranking officers and the rank and file soldiers refusing orders and mutinying against the coup that could lead to a more positive image of the military emphasizing common soldiers as the defender of democracy in its most dire hour.
You might also see much more overt and direct efforts to fight fascism abroad. A failed fascist coup at home could easily inspire a fierce desire to seek out and destroy fascism abroad. It's hard to dismiss the rising fascist tide in Europe as, "someone else's problem" when American fascists try to make that happen.
This would certainly leave the isolationists & America first political philosophys with fewer wealthy patrons. Still the disillusionment with the outcome of the Great War still ran deep in the US collective psyche. That could still prevent the US from rushing off the save France yet again in 1939.
I dont know the complete history of US financial backing of Germany. By 1935 Roosvelt may had ceased to policy of helping Germany obtain loans. If not then a failed B-plot would go a long ways in ending the US as a loan broker/guarantor for Germany. Down the line in 1939, 1940, 1941 the nazi government would find a lot less in the way of business partnerships between German private & quasi public companies and US businesses like Chase Bank, Davis Oil, DuPont, Ford, Standard Oil....