Big cities became big over time due to their location. For NYC it has always been the docks and stock exchanges....
Then it became a self perpetuating beast....more people meant more stuff that NYC became a center for....
Shopping, fine dining, theatre, medicine, and educations......
ALL of that stuff does not have to stay there anymore.....telecommunications have made the location no longer relevant.
The exchanges have left....
The banks right along with them.
Theatres?
Medicine left....been gone.
Education?
Hotels....fine dining?
Why need a hotel if you dont need to travel there?
Nice food fit for a king? Dont need that either.
I used to like NYC.....you could get anything there for a reasonable price....but everyone is either gone or in process of leaving. Urban flight and blight.
Without the titans of industry and trade NYC is a filthy city with no redeemable features.
The second rule of being a grown up and adulting is that Government can't do anything to create an economy....but it most certainly can destroy one in a hurry.
American people have ALWAYS been the greatest resource ......
Without them....you just have a disaster zone suitable for a UN crisis center.