how would it know the speed limit? Read speed signs? Google map?
I recently drove a 2021 vehicle had camera(s), apparently reading roadside signs (which have a standardised format in the UK) and white-painted signs on the roadway. This system would fall apart if, for instance, New York State and New Jersey had different styles of roadside signs....
Additionally, but unconnected to that car, I have an app on my phone, Drivescore, which monitors the behaviour of my phone, and hence my driving, in terms of speeding, acceleration, braking, cornering etc. Those who score smoothest and safest qualify for insurance discounts with the insurers who embrace the system. The informational blurb for this app states that it has an extensive database of current applicable speed limits in the UK. I assume that info is held at Drivescore central, and the app communicates with it at intervals.