I said Korean's cared.

If they are not putting signs in the US (I don't live there) they are failing, or the motivation is not safety but money.

In the USA, speeding tickets are about revenue, which is why they hide their speed traps.

In the UK, fixed speed cameras are often preceded by warning signs. Not so in Australia - I think we've had cases of them being hidden in roadside bins. It's common to see a police car with speed gun behind bushes at the side of the road.