How often do you reach for the hazard button when stopping for a construction zone? Except in cases where the first guy panic stops, most such accidents are because the one behind was somehow distracted by any number of things - only takes a sneeze-worth of time ...
I drive in a foreign country a lot of the time.
Horns and hazard warning lights are well-used (and often-used) pieces of the vehicle’s equipment. They certainly have applicability in the USA to a greater extent than they currently are employed. IMHO, of course
If I’m last in a construction zone with a work stoppage (or very slow movement), I always put the 4-ways on. I’ve driven close to a million miles, mostly on interstate, and everything I’ve seen and learned says outside the flow of traffic do everything you can to make sure people who aren’t expecting a stop see you.
My drive is off a 45mph road (going speed closer to 60) and I always flash my brake lights several times to make sure they’ve noticed I’m slowing down.
As a defensive driver, I’ve avoided a lot of accidents (even pulling off the road for a big rig that couldn’t slow down in the snow), because I don’t want to lose my old car or my life!