I think last time the truckers were saying that 55 wasn't their optimum. The gears in an OTR tractor don't like 55 last I heard. They once claimed that 65 was the most efficient speed on level terrain with no head wind.
What do I know, I don't drive truck except my PU which does much better at 55. I'm driving about 60 these days, but I pretty much have always used the 3rd lane on SoCal freeways and kept the speeds down. Most of the time that's a moot point.
I could live with a national 55 speed limit. If I want to go fast, I'll find a place and time to do that and I do. Commuters who drive 10 miles to their destination would arrive within less than a minute under clear conditions. With traffic signals and such, it's probably a wash.
Don't get excited by the drivel.