As the famous line goes, a statistician is someone with his head in the freezer and his feet in the oven who'd say on average his body temperature is normal.
What you say and the fact that there is a lot of capita in NYC seems to me to mean the emissions are pretty bad.
No, what it means is that if those people went anywhere else, total emissions would increase because other US cities are not as well-equipped for helping people live without the use of personal vehicles, which are the major emitters in the US.