Maybe not in the US, but in both France and China, to name two countries I've been to, speed cameras were obvious on the highways and actually sent out fines.
There's a difference between having a speeding camera every now and then on the highway or consistently enforcing speeding limits.
I don't have a statistic on this, but my gut feeling would be most speeding happens in residential areas with low speed limit, and enforcement in many places is basically nonexistent.
In my experience, speeding is prolific and not tied to speed limit. I’ve read it’s actually tied to visual or physical cues the driver perceives as making speeding riskier or safer. Narrower lanes or walls are associated with slower speeds.
I don't have a statistic on this, but my gut feeling would be most speeding happens in residential areas with low speed limit, and enforcement in many places is basically nonexistent.