"I think it was quite clear to them that they did not land at India. If it wasn't immediately, then it became clear shortly thereafter. My guess is that the term "Indian" came from the people who heard/saw Columbus travel back and have never seen an actual Indian in their lives."
Think of it this way, Columbus was sailing blindly to the west. He just assumed india was the closest one could go. What proof did he have that a New World even existed? By the best of his knowledge, he believed he'd hit India.
Oh please...it's not as though no one had ever been to India before. The description alone should not have matched what he saw when he landed.
From every history lesson I've heard, it's been said that Columbus, to his death, thought he'd landed in India.
It was quite obvious that India is not the same land as what would become the Americas. Every history professor I've ever had can tell you that Columbus was not so thick-headed, judging by his behavior outside of that in the shitty elementary school lessons.
Perhaps Columbus wasn't as bright as you believe. How many times had he been to india before? Was he a merchant? A cartogropher? He didn't land at any known port town, and it's highly possible that isolate tribes could bear very different cultures.
I highly doubt that, even if the people are genetically related at some point.