The camera is "critical" to manufacturers by definition because it's the subject of regulatory compliance - it's a must have for the manufacturer to clear a gate.
We also know that people have been driving in all sorts of conditions and in all sizes of cars without backup cameras for decades upon decades and cameras are obviously not critical to the act of driving the vehicle. They undeniably help: the field of view is often wider than your mirrors, you can drive backwards at high speed while ducking to avoid bullets, You can see directly behind the bumper of your car to wedge yourself into tighter parking spots and avoid backing over tiny people, etc. I don't believe a functional backup camera is required to resell the vehicle.
If you never learned to drive without a backup camera, it may be more "critical" to you individually.
Emissions systems are a completely different story. Critical to manufacturer and required for resale of the vehicle (technically critical to owner), though who's going to check for that $400 bypass kit? ;)
Edit: I really don’t understand why I’m getting downvotes on this. Is it because people are so glad the federal government is in their bathroom making these “critical” decisions for you?
My point is that the federal government makes all kinds of decisions that are obviously not “critical,” and that includes in the auto industry.