I think the real question is whether we can do it today.

e.g. When NYC expanded its subway system for the first time in 50 years in 2017, it cost $2.5 billion per mile. 8-12x more expensive than similar projects in foreign cities.

There might be too much regulation and too much cost and too many meetings and too many contractors and too much political conflict to do many of the feats we did in the 19th and 20th century.