Earlier quoted context omitted.
How many of those systems are owned by private people that has no idea what to do about it? Do you plan on suing half the planet?
If these systems are owned by private people then the company who designed it/deployed it is liable. If I have root on the device then it's my fault if I screw up, if I don't have root and it's just a plug and play appliance then whoever designed it/sold it can be liable. This solves the issue of "grandma buying an IoT washing machine" mentioned in another comment as the manufacturer of the machines can be sued direc…
If you pass that law on Day Zero, I claim that on Day One, manufacturers provide some horribly arcane command-line interface for rooting lightbulbs and washing machines, and add some boilerplate to their shrink-wrap licenses forcing customers to acknowledge that they have admin privileges on their devices.
Problem solved for them, Granny is liable again according to your system.