There's an enormous amount of unused, abandoned fiber. All sorts of fiber was run to last mile locations, across most cities in the US, and a shocking amount effectively got abandoned in the frenzy of mergers and acquisitions. 2 trillion seems like a reasonable estimate.
Giant telecoms bought big regional telecoms which came about from local telecoms merging and acquiring other local telecoms. A whole bunch of them were construction companies that rode the wave, put in resources to run dark fiber all over the place. Local energy companies and the like sometimes participated.
There were no standard ways of documenting runs, and it was beneficial to keep things relatively secret, since if you could provide fiber capabilities in a key region, but your competition was rolling out DSL and investing lots of money, you could pounce and make them waste resources, and so on. This led to enormous waste and fraud, and we're now on the outer edge of usability for most of the fiber that was laid - 29-30 years after it was run, most of it will never be used, or ever have been used.
The 90s and early 2000's were nuts.
For infrastructure, central planning and state-run systems make a lot of sense - this after all is how the USA's interstate highway system was built. The important caveat is that system components and necessary tools should be provided by the competitive private sector through transparent bidding processes - eg, you don't have state-run factories for making switches, fiber cable, road graders, steel rebar, etc. There are all kinds of debatable issues, eg should system maintenance be contracted out to specialized providers, or kept in-house, etc.
I so desperately wish it weren't abandoned. I hate that it's almost 2026 and I still can't get a fiber connection to my apartment in a dense part of San Diego. I've moved several times throughout the years and it has never been an option despite the fact that it always seems to be "in the neighborhood".