Serious question: what would it look like if everyone needed to live in a NYC. Of course there would be more of them, but the big cities would probably get big

Serious question: what would it look like if everyone needed to live in a NYC. Of course there would be more of them, but the big cities would probably get bigger. What would a double-size NYC look like? Living somewhere so big and crowded that officials physically press/pack people into a subway car at rush hour sounds awful to me. But folks in Tokyo put up with it. Makes me wonder if it's by choice. Honestly wonder...