I haven't talked about this with an actual Christian, but it seems to me that an erudite Christian won't hold this view that the snake was Satan, especially when you can get rid of the contradiction by saying the snake was not Satan.

My highschool theologist said that "a demon" (not necessarily Lucifer or any demon whose name is known) spoke through the snake. So I imagine there are a lot of open ways to resolve the contradiction:
- Perhaps the snake is punished for allowing the demon to control it in some manner.
- Perhaps only the particular demon is punished in this manner, not the whole of demonkind including the one that later tempted Jesus.
- Perhaps the description of the curse/prediction is metaphorical, so "on your belly you shall go" is a metaphor of the demon living a filthy existence or something. After all "And I will put enmity between you and the woman, and between your offspring and hers; he will crush your head, and you will strike his heel" is supposed to be metaphorical of the Crucifixion and Resurrection.

etc, etc.