New York City is actually not a good location for a modern, dense city. The preponderance of rivers is problematic, and makes transit a lot more expensive than it would otherwise be (just look at the cost of new rivers and bridges). Manhattan, Staten Island, and Brooklyn and Queens (on Long Island) are all islands.

Houston and Dallas have much more amenable geography for becoming denser, larger cities with better mass transit. Yet they haven't, because they chose not to.

And there's plenty of unused space in New York state, anyway. It's big and only moderately populated north of the Tappan Zee Bridge. Compare New York with Texas: https://upload.wikimedia.org/wikipedia/commons/e/e2/New_York... https://i.redditmedia.com/cn1OstwGd24Katakx1DFdC8cVzAjUVyOFh...