NYC has more resources to function than just about anywhere. High tax, both state and city, combined with a massive number of taxpayers. Extremely high road and bridge tolls. Best-case, near-universal ridership of the long-established public transit (and significant rider fees). Very small land area over which to spread its city income.

If they can't maintain a clean and tidy city with the resources they have, the taxation and manpower required is probably not achievable.

I think that unless you have a non-American (e.g. Japanese) community caretaking ethic that comes with other baggage (and can't easily be recreated in American culture), the residents will wear it down and trash it faster than it can be fixed. If you put 10m rats in a proportional land area, they'd kill each other - I don't know why we think it's healthy for human habitation to exist at that level