From my work travels and the people who I’ve worked with abroad, I would say most of the Premier league teams are equally followed I’ve seen knock of Arsenal/Chelsea (fake) shirts in the most remote places. Some kid selling water melons at a bazar or some kid on a back of donkey in some village, or some kids kicking a ball about in the middle of nowhere.
Most of the places I been to though Barca and Real Madrid dwarfed all the other teams, especially during the Messi Ronaldo days. Places would be shut down, hundreds of people gathering to watch to together, it’s funny because in Iraq I’ve seen groups of people fighting over the teams when one loses, like full football factories kind of skirmishes, in 2006 a group of Brazil fans clashed with some French fans, which unfortunately resulted in the deaths of a couple of youngsters. Football is actually so big I remember during the World Cup final, you had no explosions or shootings in the city of Baghdad (none that were reported anyway) it was like the whole country terrorist groups in all were watching the game. Total madness.