I never liked superheroes comics and can't really answer your question, but one thing is sure: many people all over the world love movies based on superhero comics.
I for one always wondered why Franco-Belgian comics are not successful or not published at all in USA (don't know about Canada - they might be published and successful in Québec). French and Belgian artists made the best Western comics after all (e.g. Blueberry, Durango) as well as many of the best and most influential Science Fiction comics (e.g. Moebius' works which influenced e.g. Blade Runner and Alien, Valérian et Laureline which influenced the Star Wars design), not to speak of hundreds of great adventure comics, funnies and semi-funnies (Astérix etc.), but most North-Americans never heard of them.
Manga are the only regional comics that managed to conquer the whole world (but even they didn't manage it before the 1980s).
A possible answer to your question might be: worldwide publishing limitations in the early days and superhero comics being a genuine North-American invention and phenomenon (though the latter theory doesn't explain today's enormous worldwide success of superhero movies).
