Part of what I (or you) am (are) likely not getting here is that the US itself was teetering on lawlessness, and the years of violent "shoot em down in the streets" towards the perpetrators of labor union rights e.g. were to follow in the near years following the Senate Isolationist LoN votes to which you assign the blame for the 50-80m deaths from that conflict.
The US was far from a mellow armchair democracy.
To assign a bit, any or all of this to the US Seante dumpin the LoN (while agian very very popular) simply seams to me to smack only of lazy armchair liberalism. Mind you, I am lazy, like armchairs, and am a liberal.
I do not see a full construct on the other side. So, the Senate ratifies the LoN .. and ... uhhh, then the US mobilizes to put troops in Czech?? or what .. I mean where is the magic? The depression was realy bad, probably worst in central europe, and guess what, they started killing people. Wash, rinse, repeat.
Votes in the US senate had little opportunity to amend that.
Fiscal blame? Austerity blame? Dunno, don't do books, seems pretty much everybody's books were pretty bad.