The weird thing is that in Germany you have these competing speeds that make driving worse for everyone. That 20kph difference is responsible for a lot of bad behavior on smaller roads. On the Autobahn the differences are even bigger, even if there's more space (a second lane) but then like you mentioned there is a lot of traffic.
In the US and Canada for example the speed limit is just the same. Everyone goes at 100kph in Canada, truck or no truck. While you have people speeding there as well obviously, everyone is sort of going at the same speed.
in NJ, everyone is going about the same speed, but way over the limit. people seem to be pretty good about staying out of the passing lane in light traffic.
in VA, everyone does seem to more or less go the speed limit.
in MD, it's utter chaos. you'll see a minivan going exactly the speed limit in the left lane, people passing it 10-20 mph over the limit, and wild people weaving in and out of exit lanes to pass everyone else at even higher speeds.
In the US and Canada for example the speed limit is just the same. Everyone goes at 100kph in Canada, truck or no truck. While you have people speeding there as well obviously, everyone is sort of going at the same speed.