The initial question of this thread should be clarified, the first interpretation is "is there a lack of asian heroes in western media", the other is "is there a lack of asian heroes in all media, worldwide".
To the first, the answer is pretty much "yep". There are some asian heroes in western media, but not too many, and most of those are obviously token characters. (The first that comes to my mind was the super samurai character from the old superfriends cartoon, alongside other token characters like black lightning and apache chief.) The ons I can think of offhand are jubilee of the xmen, silk from the spiderman comics, red sun or something (a japanese guy with heat powers), and the afforementioned super samurai. Asians much more commonly appear as villains in western comics.
To the second interpretation o fthe initial question, the answer is definitely "nope". Japanese media is chock full of japanese superheroes, from super sentai and kamen rider to dragonball, and others which are more debatable. (Does naruto count? Everyone in it has supernatural abilities, but 1) they're framed as common ninja abilities and 2) literally everyone has them. To paraphrase someone; when everyone is super, no one is super.) Chinese and korean media also have people with super powers, those these are most often in the form of traiditional martial arts abilities like chi.
All countries and regions have their own sets of superheroes, they just often seem like they don't because 1) people from outside those regions are often unaware of local characters and 2) cultural differences. Re #2; First there is the question of what exactly is a "superhero". For example, super sentai and it's ilk seems more like just cops or soldiers or something, but if you look a bit closer you'll find nearly all the common superhero characteristics. Secondly there are differences in the actual media. Japanese media for example usually tells a story and then ends, unlike american media which continues indefinitely until it stops making money. How is this relevant to the current question? Because american style media results in a few monolithic heroes, whereas the japanese style results in a lot of smaller heroes which each get much less public attention.