As for the Northerners that are described as unfriendly, it is more of a space thing. If you invade their space or ask questions that are out of line and you are from another part of the country, it does seem rude. One thing I have learned is that North Easterners are intensely loyal, but you have to prove yourself worthy of their trust, they don't take just anyone into their inner circle.
The rudeness and the rushing are found in any large population area, the speed meets the need. More people must be served by businesses and there is only so much room for each person or business, while they might like to stop and chat, they have to keep up with the pressure of serving a higher volume of people. I've found that even thirty minutes out of big cities that it slows down a lot and becomes friendlier.
My experience is mostly living in the Mid-West, I find people exceptionally nosy and gossipy because they are too free with information that should be private or semi-private. I find that ones is also more likely to run into people with nothing better to do than intervene where they are not needed or wanted, especially white suburban women who like to call CPS.