I would say the strongest example is wired telecom, which may not be a national monopoly but is certainly a local monopoly across nearly the whole country. The way the companies divvy up territory to avoid competition is probably what keeps U.S. prices so much higher than, say, Europe. I wonder if a case could be made for it being a cartel.

But yes, cellular and satellite providers have started to provide a saving grace of disruption in that market. We'll see if it ends up being enough.