The most likely answer is that NYC was just a good place for it to spread which had plenty of travelers to get things started fast, but that that the death rates aren't particularly high -- everywhere that has fewer deaths has just had less of their population infected ... so far.
Germany has about as many cases in total as NY, yet less than 1/2 of the deaths. The death rate seems high in NY, maybe because hospitals could not cope?
Germany has about as many diagnosed coronavirus cases; the difference could be wholly explained by Germany testing more people. (Germany has administered 2 million tests, New York State [I didn't see a figure for the city], about 700 thousand.)
