Yes, good catch. A driver's side mirror is required, passenger's side is optional (but recommended). But, there is some lobbying going on right now to allow cameras in place of mirrors (GM specifically is trying to get the new Corvette C8 rear view camera approved, which I'm guessing won't happen for launch in early 2020).

There are cars going on sale in the EU market (Audi E-tron, Honda E) with cameras replacing the side view mirrors. Presumably at some point these will also be allowed in the US.