Your own example, Bell System, is an example of an sub-optimal but obviously adequate regulated monopoly that worked moderately well over a century.
And US Steel certainly did _not_ have competition when anti-trust was brought against it. By 1907 there were no longer any competitors and anti-trust attempts only started in 1911.
What you do have today, for adopting pro-monopoly policies for decades is, among other things, the highest bandwidth prices in the developed world. Higher even than the comically inept regulated monopoly Telefonica. Which btw has phone plans and per minute charges a fraction of the US and where the idea for charging for an incoming call is unthinkable. And a food supply monopolies that inflates the price of food to stunning levels. The list is endless but my typing patience is not. So here's a link.
http://www.economist.com/news/briefing/21695385-profits-are-...