> FedGov would have to evaluate or interact with every sort of intra-state interaction

I don't think that's the case. It would be up to Congress. They have the authority to pass a law that says: "No state may put up any intra-state barriers to commerce at all", and that would be that.

Or they could choose to pass a law that's a lot more specific, in which case they would need to deal with each intra-state interaction.