In the northeast, people are kind but not nice. They'll help you out when you have flat tire but may grumble under their breath that you might need to learn how to change your tires yourself. It takes a long time to get to know them, but once you do, they'll take their shirts off their backs for you.
In the pacific northwest, people are nice but not kind. They'll be super polite to you but when you ask for help or ask to hang out, they'll snub you. They're mostly homebodies and they already have enough friends, no room for more.
In the midwest, people are kind and nice. They'll help you out and they'll invite you to their homes for a meal. But they are somewhat cautious of outsiders.
In the south, people mostly just have a nice façade that is skin deep. They'll be nice and friendly to you and talk to you all day, but they may not care that much for you at all. Their friendliness is more about them wanting to feel that they are nice people, and less about them actually caring about you. Many will talk behind your back ("bless your heart" culture).
Terms like Seattle Freeze, Minnesota Nice, Southern Hospitality are all overgeneralizations and don't apply to each individual, but nevertheless capture a part of the culture that is at least somewhat true.
For instance, a 2008 survey showed WA state ranked 48th out of 50 in trait extraversion. Seattle definitely feels socially different from other places -- it is very palpable.
Here's the paper ranking 50 US states on the Five Factor model (Extraversion, Agreeableness, Conscientiousness, Neuroticism and Openness)
https://pdodds.w3.uvm.edu/research/papers/others/2008/rentfr...