Hola Willen,
Be aware of this: people living in USA refer to themselves as "americans". The rest of us, basically in all Latin America, we know we are "americans" because we live in the continent that we call América, whether "Sudamérica" "América Central" or "Norteamérica" but we use to refer to ourselves the nationality that corresponds to the country of origin. In my case, for good or for bad, I am "argentino".
So, if you refer to "Americans", depending who reads it, could have a different meaning. So, again , "original Americans" could mean something completely different for who reads it.
Just for your reference, if you search with time and patiente, from Ushuaia to Alaska there were many different cultures at the moment the Spaniards came to this side of the Atlantic for the first time ("discovery" as it is called).
From the top of my head in no specific order, search for:
diaguitas
aimarás
toltecas
olmecas
comechingones
onas
athabascan
charrúas (we are known by the use of the expresion "che", coming from their language)
guaraníes
tainos
araucanos
tehuelches
mayas
iroquoi
pilagás
cherokee
I could go further. There should be about 50 to 70 more that I mostly could not recall. Most of them were NOT "red".
And yes, it seems that the Bering stratit was probably the first access to these lands. And that was many many years ago. According to what I read, along the centuries, people moved slowly South down to Ushuaia.