I kind of think that it has more to do with being "urban" than with being in the Northeast. Maybe cities drive us crazy, and nature restores sanity. Or maybe we are like rats - when the population density gets high enough, we start attacking and eating each other.
When the population density is high enough, you bump into scammers and rude people and outright criminals often enough that you expect them everywhere. And that's true even if the percentage of ratfinks is constant everywhere.
But I believe that once people see rotten behavior in their neighborhood fairly often, they start to think "everyone is a bum!" or "If I'm the ONLY nice guy, I must be a sucker". Then the percentage starts going up.
As with insane drivers, we mostly don't notice the 99 people on the sidewalk who are normally polite. But we remember for decades the one person in a three-piece-suit who elbowed grandmothers out of his way because he was "so important" (in his own mind).
In the PNW, aggressiveness in drivers seems to correlate with distance from a major city, and perhaps with population density.
