For a wonderful example of team-on-team petty, we look to the southeast. (And, to clarify, this is an extremely abbreviated version of events.)
In 2017, Atlanta United pushed hard to make their first game with
Orlando City matter because I’m not sure they realized that
the entirety of the league would find them insufferable by April and they needed a common enemy to rally behind besides...everyone.
To stoke things, they bought a billboard in downtown Orlando informing the city they were “Coming to Conquer” (below).
That same year, Orlando’s Supporters’ Groups were banned from returning to Atlanta for a number of games. Orlando would later retaliate by doing the same to Atlanta. Atlanta would later beat Orlando in Atlanta and play a song from the Lion King over the sound system immediately following the final whistle. Orlando would later geoblock the entirety of the state of Georgia from buying tickets to the 2019 U.S. Open Cup semifinal.