Soooo I'm from Houston Texas... Been here all my life and have never gone to a State up North (like New York)... But I've encountered several people that are from the North and they seem to be a bit more aggressive or rude(r) than what I'm used to. I've also heard some of them say that people from the South are "too nice" and say "please, thank you, excuse me" etc more than the Northerners. I know this isnt the case for everybody but just in general...
As a Canadian, most of the rude Americans I've met have all been from the South. Most of the time when I go to New York, Michigan, Ohio, etc. they're all extremely friendly and often very helpful. My parents also make remarks on how they hate visting Southern states because they're always too hostile.
I think in general people from the South are more hospitable and polite, but there also tends to be more examples of overt racism & homophobia compared to the northern states, so I guess it kind of balances out.
I think it has more to do with big cities. I feel like there are more big cities in the north than there are in the south (I could be wrong) and it always seems like the bigger the city is, the ruder people seem. But as someone said before, life is more fast-paced in the North because of the bigger cities, so people don't have time to worry about being polite.