I think there’s some conflation of issues here - racism definitely requires a racial/ethnic element. It can’t just be about nationality (that’s xenophobic), geographical area etc. Saying (for example) that Norfolk is a backwater full of inbred weirdos is not nice, it’s prejudiced, discriminatory and hateful (if delivered with any venom or hate), but it’s not racist.
Hate is hate - so I’m not advocating any such behaviours. But I think one of the key differences is that ragging on a neighbouring city/area can still be done in jest as long as everyone is having a laugh. I enjoy the odd dig at some Barnsley folk about having 6 fingers (and the like) but I deliver it when I’m with my mates from that neck of the woods so I know they get the spirit of it, and I know full well they’ll give as good as they get.
Conversely - racism in the UK has reached a point where you don’t joke about it, doesn’t matter if it’s well intentioned. I’m not knocking that because far too many actually hateful people try to disguise their racist bigotry with “humour”. Better to throw the racist jokes baby out with the racist bathwater.