About evenly spread both sides of the Iron curtain, I’d say. Lots of demoscene in eg Germany, Scandinavia too. Netherlands, UK and France also have sizeable (though smaller) scenes.
Assembly, arguably the most known demo party, was famously Finnish. Future Crew (who made Second Reality) were (are?) Finnish as well. Lots of demo scene in Germany, also.
There were a lot of global crews during c64 days and a few crews on the Amiga. In New Zealand on the Amiga a lot of the warez and compilations had importros on them. So was a small coding scene here but not as big as Europe or during C64 days.