I trained and got licensed in the US. It never even entered my consciousness what "undertaking" is. We do learn that left=fast, and right=slow, but pretty much nobody observes that rule on the road. The behavior is the same across all states. People drive and pass wherever they want.
It's nowhere as bad as something like Brazil, in global context. But it'll drive a German or Swiss mad. Think of something closer to Naples, without all the scooters zigging around.
I visited the US a few years ago with my parents and we drove over there from Chicago to Lansing, MI, then over to Sandusky, OH. The few things I noticed about driving were:
1. People 'ping pong' in the lane A LOT, it's terrifying driving by them. That's rare here, but maybe only because the lanes are narrower so you can't afford to do it.
2. Brake lights everywhere, but maybe that's because most US cars are automatic so there's not much engine braking? Friends following me in my M3P get confused because it looks like I'm braking all the time from regen...
3. Like you said, people just drive wherever they want to.
4. At least 30% of people are using a phone whilst driving.
In the UK, undertaking can get you 3 points on your license and is really frowned upon. Using your phone is 6 points and sometimes a driving ban. (12 points = License revoked)