Well, yes, and, also, not really. First off, yes. Indeed. Believe it or not, manga is manga, it means "manga," and unlike the word anime アニメ, which is used for things which we wouldn't call "anime" in English, all manga is pretty much just "manga." However is all "manga" manga?
Disregarding details like comic strips in journals and yonkoma 四コマ, which are comics with always and only "4 panels," are manga which we'd call "manga" in English always called manga in Japanese and only ever called manga in Japanese? Actually, no. Ironically, manga is more often than not called "comics" in Japanese!
Yep. You heard it right. Synonym with manga 漫画 is the word komikku コミック which, as you might have guessed, comes from the word "comic" in English. Worse yet, the word komikku is more popular than the word manga in Japan!
For example, the largest doujinshi fair there is is called komiketto コミケット (website). Not mangaketto or doujinketto. Komiketto.
That is not to say the word manga is not used. It is. It's just that komikku has a nicer ring to it than manga, so it's more popular.
Why is komikku used instead of manga?
Now after all this newly attained knowledge you might be thinking: what the fuck is wrong with these Japanese that they are using these baka gaijin words to talk about glorious nippon manga?! Well, the answer's actually pretty simple.
"Comic" is an English word.
That's basically it.
No, I don't mean that historically comics were invented in England or the USA, that makes no sense, I mean the word is not in Japanese, therefore it's cooler, more kakkoii カッコイイ, than your usual Japanese words like manga 漫画. Also, katakana カタカナ letters look cooler than kanji 漢字.
To look at it from another angle, why are you calling Japanese comics "manga"? Do you call Korean comics... you know, whatever they call comics in Korean? Or French comics the word comic in French? No? So why are you calling Japanese comics manga? Why aren't you calling Japanese comics komikku like the rest of the Japanese people?