Still reading through the thread, but I think that's unlikely. LaRouche's OTL political radicalization began during his service as a medic in the US Army in India IOTL--the birth of his anti-British leanings (for obvious reasons), and also his turn to Communism. Without American entry to the war, LaRouche might not be exposed to the right ideas at the right time, so he remains basically a Quaker pacifist as he was in his youth. I just don't see a guy who already had anti-imperialist sympathies embracing the Reich. His peculiar philosophical interests might still be there, but everything about them indicates that he would be completely hostile to Nazi ideology.Fair enough re: Rockwell (though I think he still very likely would develop Nazi sympathies and I thought he was Virginian).
Actually another dark horse option who was born pre-departure has come to my mind: Lyndon LaRouche. Now he began in OTL as a far-left figure but his brand of far-leftism over time horseshoed its way towards far-right sentiments and given he jumped left amidst the Cold War OTL I could see him instead embracing American Nazism rather than Trotskyism on grounds of contrarianism plus his anti-British beliefs and anti-Semitic leanings. I could easily see him ITTL joining the German-American Bund or a similar group in lieu of the radical leftist ones he joined OTL. Especially since the Axis victory could discredit Marxism to a 20-something LaRouche and that timeframe was when he developed his beliefs.
Most likely outcome for him ITTL: low-level intelligentsia, possibly a local college philosophy professor, who gets offed in the general purge of intellectuals when the US is conquered, particularly because of some papers he writes in the 1960s condemning Hitlerism as an expression of Aristotelian anti-humanism.
More heroic outcome: organizes a local branch of the US resistance in the industrial northeast, killed by the Gestapo in the 1970s.
More villainous outcome: Collaborator who sells out his colleagues and ends up garroted by the American resistance in the 1970s.