Here in Florida the state law is that you put on your headlights when the first drop of rain hits your windshield. Not that most people bother. But maybe more than anywhere else in the continental US, 3 raindrops can turn into a torrential downpour in a matter of seconds.
Very few American drivers take "Drive Defensively" to heart. (My personal variation on that is "Driving Is a Team Sport".) thickjohnny, you may remember the "DD" PSAs from when you lived in the States before. But nowadays hardly anyone knows what that phrase means and most drivers are much more concerned with themselves than with any other cars on the road. Misaligned headlights or inappropriate lights on? The other guy's problem. I think that most people using fog lights on clear roads have them on because they make them look badass, or they're left in the default position to go on whenever their headlamps go on.
The last 4 cars I've owned have had an "automatic" setting for headlights, so quite honestly I rarely ever think about touching the lights switch in my car. Set and forget.
As for rear fog lights, US-built cars don't have them and the imported cars have them disabled. Most Mercedes and BMW models have either a setting for rear lamp that doesn't do anything, or a different headlamp switch assembly that lacks the setting. When I was in Belgium rear fog lamps were a big deal, but few Americans know what I'm talking about.
What about Americans who drive with their parking lights only, because it's "just dusk"? That'll get you a ticket in a hurry in Europe, but it's perfectly fine in many US states.
Turn signals in theory should be used, but most people don't bother. Here in Florida I know people who have forsaken their use altogether, because it alerts other drivers to do insane things like rush to cut you off. Happens constantly. I admit that I calculate whether it's worth it to use my indicators when changing lanes based on the likelihood I'll
just be giving the guy in the lane over some incentive to squeeze me out. It seems to be a point of macho pride around here (Miami area) to never, ever let anyone get in front of you. The instinct to cut people off has become reflexive. Zipper merge? Fuggeddabouddit.
When I was learning to drive in high school (Virginia), I took Driver Ed in school, private lessons, and also practiced a lot with my parents. Got lots of good advice with emphasis on conservatism and courtesy. We did a lot of highway driving on I-95 and the Beltway, and I remember that one of the courtesies I was taught was that when an 18-wheeler passes you after dark and then wants to come back into your lane, flash your headlights when he has safe space to do so. He will thank you by turning his lights off momentarily. If anyone does this courtesy for me in my passenger car (as some have), I use my indicator to change lanes and then give them one quick "blink" in the other direction once I'm in my lane, as thanks.
My Germans friends who visit are constantly pointing out things on the road that would never, ever pass muster at home. Things like cars and pickup trucks with hubs that stick out many inches from the sides of the body, lots and lots of stuff hung from mirrors and on rear shelves that obstruct views, and everybody holding phones. They've even appalled at kids under 13 in the front seat.
And don't get me started on the creative driving. Hardly a week goes by down here that I don't see someone in the right lane making a left turn when the light changes... right across 4 lanes of traffic (in each direction!). Virtually everyone where I live assumes it's "OK" to make a U-turn at will when you're at a red light. And it seems no one understands what a red arrow or a flashing red means. It's a wonder there aren't more horrible accidents.
It's all pretty loosey-goosey over here. As long as you're not belching out smoke or driving with various lights obviously missing, you're good.