Exactly. Rangers & Celtic's worldwide following is mostly made up of ex pats, Scottish or Irish that have relocated. They have supporters clubs all over the world, bars in a lot of tourist places in Spain, Turkey & the like.
However, they will have very little presence in the likes of Africa & Asia where a high proportion of the Social Media followers will come from.
The EPL is so big that like other parts of the world, a lot of people in Scotland have an EPL 2nd club. I myself are guilty of that. The league itself is the brand, more so than any individual club.