They have speed cameras all over Europe too, but the speed limit is often 130 km/h (about 80 mph). Most of the population of the US lives in states where the speed limit is 70 mph or lower.
Obviously this is an oversimplification, Switzerland and Spain are 120 km/h (75 mph), Germany often has no upper limit, a few places are 140 or higher. But in general it seems like most of Europe sets the limit at the speed Americans actually drive.
And int he uk the highest speed limit is 70, and in busy areas it’s usually 60 or 50 on highways from average speed camera enforcement of variable speed limits.
In towns it’s 30 and there’s plenty of cameras, for speed, red lights, bus lanes etc.
I know from experience that raising the speed will immediately raise the speed speedsters are willing to go. When the highway in my country went from 100 to 130km/h, people who drove 120 then started to drive 150.
Obviously this is an oversimplification, Switzerland and Spain are 120 km/h (75 mph), Germany often has no upper limit, a few places are 140 or higher. But in general it seems like most of Europe sets the limit at the speed Americans actually drive.