I'm not sure the French/Belgium split is that relevant for several reasons (correct me if I'm wrong, I'm French and don't want to wrongly appropriate Belgium culture):

- most if not all of those characters are french speaking

- lots of collaboration on those characters by French and Belgium author. For example Goscinny worked on Lucky Luke with Morris, the character of Spirou was created by Rob-Vel who is French, then worked on by Jijé and Franquin, etc

- though many were published in "Spirou", there were "Pilote", "Pig Gadget" and all which are French.

I think the whole concept is named "Bande dessinée Franco-belge" (at least here in France, maybe the point of view is different on your side of the frontier ^^)

Internationally they are mostly known as Franco-Belgian comics as far as I know. When people speak of specifically Belgian comics I tend to think more along the lines of Flemish Willy Vandersteen (Suske & Wiske).

From your username I guess you're dutch? Which may be relevant context to why you / people you know refer to the non-Flemish Belgian comics (and perhaps things other than comics?) as 'Franco-Belgian' if using French language while assuming that 'Belgian' without the specifier means Dutch language?

I.e. the same way we all, wherever we're from, add extra words to define stuff that's not our default expectation ("a new neighbour moved in" if they're someone from the same place as us vs. "a new dutch neighbour" moved in if they're from that other country; or buying cheese in the shop vs. buying french cheese), just as a (subconscious often) time saving measure that there's no need to give the adjective when it fits the normal expectation.

Not that I'm an expert on the international nomenclature of bande dessinée comics - though anecdotally, as a Brit (England, not Brittany haha) who grew up reading Asterix and above all Tintin, I thought of them (and think my parents called them) separately as French and Belgian respectively.

Culturally speaking I think there's very little difference and you're right. Historically speaking though, many people associate the French language with France and we get told all those cartoons/comics are French which ruffle our Belgian feathers! Not a big issue to be frank, mostly that old rivalry between neighbors where we are the little guy =)

In one book, there is a contest of potions that panoramix goes to and there is a Belgian Gaul whose potion gives him the ability to remove fries from hot oil with his hands