I think we might be working with different definitions of the term "causal structure"? The way I see it, what matters for whether or not two things have the same causal structure is counterfactual dependency - if neuron A hadn't have fired, then neuron B would have fired. And we all agree that in a perfect simulation this kind of dependency is preserved. So yes, neurons and transistors have different lower-level causal behaviour, but I wouldn't call that a different causal structure as long as they both implement a system that behaves the same under different counterfactuals. That's what I think is wrong with your GIF example, btw - there's no counterfactual dependency whatsoever. If I delete a particular pixel from one frame of the animation, the next frame wouldn't change at all. Of course there was the proper dependency when the GIF was originally computed, and I would certainly say that that computation, however it was implemented, was conscious. But not the GIF itself, no.

Anyway, beyond that, we're obviously working from very different intuitions, because I don't see the China Brain or Turing machine examples as reductio's at all - I'm perfectly willing to accept that those entities would be conscious.