I was taught from day one that slowER traffic (emphasis intentional) should keep out of the left lane. In Texas, unfortunately, unless a road has signage stating that the left lane is for passing only it's not. Therefore, passing on the right is just as common here as passing on the left. Is it good? No. Is it safe? Probably not. But it is fact.
I once drive in Vancouver. I followed the left lane rule, but I would still sometimes have drivers coming up fast behind me flashing their lights. They would only do it once or twice, in a "polite" manner. I thought to myself, "This is COOL." So, I tried it when I got back home to good ole DFW. What do you think happened? The first one got scared and moved over. When I passed the driver blew the horn excessively and gesticulated. The second one saw that I wasn't a cop when I passed, got behind me, sped up, and then proceeded to tailgate me at 80 mph with the high beams on. I thought that one was going to end badly, to tell the truth.
So, my conclusion is that U.S. drivers are selfish, rude, and care little about improving skills, paying attention, or giving a rat's posterior about anyone else but number one.