Begs the question: does everything have to be all white to be a 50s retro-future? You make a persuasive argument for enough of the tech, architecture et al being plausible but how much does these retro-future presents require the society and culture of the US* to stay like the 50s too?
No. I don't think that's necessary, and I imagine that GlobalHumanism doesn't require it for the thread. I just wanted to look at all angles.
As for energy and cleanliness, I imagine that nuclear power would serve both functions nicely. And regarding hub and spoke cities like the Garden City idea, I suppose we need urban planners who believe very strongly in that model, and who also believe very strongly in deliberately making things look futuristic.