LSL’s version is close to what I had in mind but just because I figured the earliest person was going to be born in the present day US or Canada. But the person could have been mixed - one parent of European descent with the other one a native American.
As far as my curiosity is concerned I’m going with Virginia Dare. I did not realize there was a postage stamp commemorating her. Maybe she will show up on a Goldback if Virginia becomes a state issuing them.
My problem with the question is are we using America as what would eventually become the United States of America or American meaning someone born in the Americas, either North or South?
If it’s America (USA) as the area not the country, it’s going to be Snorri Thorfinnsson, despite him being Viking-American - we don’t know the names of any Native Americans born that long ago, never mind commemorate them - hell, even if we knew his name, the Birdman burial at Cahokia just postdates Snorri.
I will suggest any idea of commemoration should take the historical candidates to be commemorated and the modern people doing the commemorating from the exact same geographic region, whatever it is.
For characters more modern than “who’s the earliest …”, it might make more sense to take commemoratees and commemorators from the same political entity, even if the boundaries of that political entity have moved since then and now. Even if that leads to anachronisms like e.g. celebrating somebody as a famous Californian from the days before California existed as a political entity. Or going the other direction, e.g. celebrating a famous Soviet who then hailed from what’s now independent Kazakhstan when it was part of the Soviet Union.
As well as an intestinal disorder! Yeah, I know the OP has been “clarified”, but if “commemorate” means their name is in common usage, it would require quite a bit to surpass Moctezuma’s/Montezuma’s revenge.