This is called "confirmation bias". When you see someone driving like an asshole with an NJ plate, you assign some broad description for them "look at this idiot". This happens hundreds or thousands of times.

Then a NY plate is driving like an asshole, and you say "look at this fucking idiot from NY, it's always the NY plates that are driving like assholes, fucking NY idiots".

So even though the NY plates are likely only a small percentage of the idiots you encounter on the road. Your brain has tricked you into thinking ALL NY PLATES = IDIOT DRIVER