New York City is about 12,591 times smaller than United States.

United States is approximately 9,833,517 sq km, while New York City (including all five boroughs: Manhattan, Brooklyn, Queens, The Bronx, and Staten Island) is approximately 781 sq km, making New York City 0.01% the size of United States.
Tip: This to-scale comparison of United States vs. New York City uses the Mercator projection, which distorts the size of regions near the poles.