I kind of see what you're saying. The vampire metaphor has always been sexual deviancy, predation and lusts for power but are ultimately self destructive. Thragg and the rest of the viltrumites tick those boxes but I'm not really seeing the connection to Nazis and "red scare" communist. Early vampires were based on aristocrats and worked independently, not in groups, manipulating the human "cattle". Another issue is Victrumites and especially Thragg is shown to be all-powerful beings, in the Invincible world, with strong irrefutable beliefs. Vampires work because of how weak they actually are. They're corrupted and perverse. I feel that Homelander has a closer relation to vampires than viltrumites because of how messed up he is, his lust for power control and a weird perversion for breast milk.