I’ve worked out how to do this cleanly (I hope). The data forms for clubs and festivals now include country and the map location can be entered as [UK Postcode], [Town, Country], or [GPS Coordinates], and there’s a link on the form to a FAQ page that explains each of those things including how to get your GPS coordinates from Google Maps.
Next step is whether the way the map describes events is relevant to the kinds of events you’ll find in different countries, but it’s always a work in progress and I look forward to feedback.
So if you know of events anywhere in the world put them on the map or ask the organisers to do it.
(Thanks to Maria McAlister of the Arts Council, Northern Ireland, for prompting me to see how I could make this change)