Covid is much higher in deep blue cities and regions.  That could also be due to density of their cities.  Restrictions are so bad that anything else seems welcome.  

New York City has 8.3 Million people and Miami has 5.5 Million people.

But New York City's lockdowns are much stricter than Miami's and their number of deaths are also a lot greater than Miami's too.

But New York City is also a sanctuary city and home to a lot more homeless than Miami as well. These two factors may also have something to do with the larger number of COVID cases & deaths in New York City too.

FWIW

NYC has subways. Miami has cars.  

Propagation on subways is a possibility, but then again, Japan has oodles of above ground railways and underground subways.

However, the majority of propagators are those from 16 ~ 29 years of age. And of those, the ones 22 ~ 29 are well known for frequenting drinking hot spots which have been discovered to be spreader sites... (i.e. not the trains or subways).

But in NYC, on a subway with some no mask individuals... I could imagine that would be one possible spreader situation.

FWIW

Subways in Japan are as clean as a private home.  Subways in NYC were filthy and dripping with mold.  They have been steam cleaned since then and are considered to be much safer.