I can’t really say New York City is the rudest city in the United States because I haven’t visited all of them. I went to a Columbia University in the mid 1950s for a number of years and was shocked at how New Yorker spoke to each other in traffic. They can also be amusing companions. I’ve had a number of very polite New York friends whom I like very much, but I have to admit that New York City residents in general, when dealing with people they don’t know, are the rudest people I’ve ever encountered in my eighty-seven years. I’ve found that Brits can be rude to each other too, and pass it off as banter.
I might add as a Southron, an armed society tends to be a polite society.