A man in Russia has done something that would not be possible in America: He built his own private subway system, entirely on his own Soviet-era pension money. Not only that, but he also got all the correct permits and so on, and is legally backed by the Russian government.
Mr. Murlyanchik, the subway builder, has been at this since his retirement in 1984, and has been extending 1 meter per day since then. He has built it so that his neighbors can have stations if they request them, and plans to soon have automated cars capable of carrying 3-4 people patrol the rails that he is now placing in his elaborate network of tunnels. (His tunnels are narrower than commercial subway lines, and therefore of slightly lower utility.)
Also impressively, he has dug under a number of roads that have 60-ton trucks running across them, and his tunnels support that weight easily. This is a man with deep understanding of earth-engineering.
I say that this is not possible in America because here property rights extend from the surface to the center of the earth, and to dig under any other person's plot of land would require their explicit permission. So the subway would have to follow only public roads and lands, and even that would require explicit government permission, of which they are not likely to grant. Also, goods in America are expensive, and the average retiree likely could not afford the thousands of tons of cement that this would require.
I begin to wonder if Mr. Murlyanchik had additional sources of funding, could he reach all the way to Moscow?