I doubt that it would be possible for them to get enough resources and popular support to wage an effective guerrilla war. I could be wrong, but in my opinion the chances are slim.
It seems to me everytime I propose the idea a group wages guerilla warfare, people hit me with that same phrase.
Many Soldiers and officers, and even scientists that hadn't been caught by the British or Americans had come over here.
Some Men convincing enough down-on-their-luck immigrants that Nazism was what they should believe in and you could have a militia within a decade, (which does render my original fictionous tidbit implausible at best).
If you don't believe people aren't desperate enough to give into those Aryan supermen ideals, remember, thousands are still believing in Seventh Day Adventism (which is stupid at best).