Ok, let's look it it in a bit more detail. IOTL Butler testified in November 1934, let's say here, that's when the plot is executed.
General Mosely's time as Deputy Chief of staff ended the preious year, but he may have some contacts he and the plotters
deem useful. If we assume a Valkyrie style flash in the pan, what's the fallout? We're probably looking at one of the most
infamous events of the 20th century, one that will probably be branded into the American public consiousness.
Mosely, being guilty of mutiny and treason, will almost undoubtedly be shot, and the other consiparitors will
probably be tripping over each other in a rush to testify and get themselves off the hook. Either that or close
ranks and hang Mosely out to dry. If we assume that all the senior officers named in Butler's testimony were
active conspirators, they'll probably loose their commissions at the very least.
Fascist organisations would almost certainly be banned, although the definition of such could be extremely broad.
The popular backlash against far right politics could affect views on the new deal (Hey, at least the socialists didn't
try to overthrow the goverment). This could embolden the government itself with regards to economic policy.
Foreign policy however is another matter, the Americans would be extremely wary of fascist governments
within their own sphere of influence, perhaps resulting in an early form of "containment". Maybe a popular,
later official boycott of German, Italian, and later Japanese goods? Taking Jewish refugees?
Relationships between the Roosevelt administration and the fascists governments of Europe will be strained almost
from the very beginning. The antipathy to fascism at home and abroad might even generate sympathy for the League of
Nations, althought this is unlikely.