when it comes to social distancing in public places, quarantining when coming from states with lots of cases, and wearing masks. New York has had 243k confirmed cases. They have a population of 8.4 million. Even if the number of cases were 20 times higher than confirmed cases that number is still below the 60-70% range that is required fore herd immunity.
Let's say that only 10% of cases show symptoms which is the lowest the CDC lists here:
https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html
That would mean that New York has had 2.5 million with it which is still substantially lower than herd immunity. New York is doing well because they have some crazy ass rules.