In poland, if someone has lights set too high or too bright, many drivers will blink with high beams. It's annoying enough that people with bright lights have set them to appropriate level in short order.
Unfortunately, the response here in America seems to often be, "Fuck you, buddy. Look at my actual brights"
Some people have taken to flashing anytime they find your lights bright, even if it happens to be the moment they are in the center of the beam pattern due to things like hills. I can understand the temptation to retaliate with "No, smartass, this is what brights actually look like."
Around here, it's often very difficult to tell if the oncoming lights have flashed in your eyes because someone's deliberately flicked their high-beams at you, or because they've just gone over a bump in the road, exacerbating this problem.
That's not been my experience. Every time I flash my highbeams at somebody with their highbeams on, they turn theirs off. Most people (yes, even most Americans!) aren't being deliberately malicious. Forgetfulness is much more common.
We are talking about people whose non-high-beam lights are blindingly bright.
And I'm saying I've never experienced any sort of retribution for flashing my highbeams at people with bright lights (which I do habitually.) I'm sure it happens to some people some times, but it's clearly not very common.
I think a nicer interpretation is: "I'm sorry about my bright lights, but I don't accidentally have my high beams on, thank you."
European cars are also required to be able to change the angle of the lights. Even my super basic 2007 Skoda has it.