For (at least within scanlation scene) english usage:
Manga is comic originated from Japan
Manhwa is comic originated from Korea
Manhua is comic originated from China
"Tank is an armored vehicle originated in the UK, char d'assaut is an armored vehicle originated in France, Panzer is an armored vehicle originated in Germany." It's fine to call them all "tanks" and it's fine to call all East Asian comics "comics" or even "manga".
I can see the logic of calling east asian comics "comics". But why would an English speaker use a Japanese term, "manga" to refer to all east Asia comics?