The African-Americans differ from their African ancestors because of two things:
- they are a mixture of several African people
- it was quite common that an American slaver impregnated one or several of his slaves, so many African-Americans do also have European ancestors
But the European influence in the heritage of some North American tribes are much older than the first arrival of Europeans in America.
You're using a circular argument here.
Afro-American genetics european heritance is more recent than amerindian one, because european came sooner. And we know that european came sooner because the DNA show that afro-american one is more recent?
For the mixture of several african people, as the european ones, the DNA difference is minimal.
The two continents knew an really erly genetic brassage, and you can't tell only by DNA which guy are from which people.
The DNA of Afro-Americans is distinct from african ones because of european legacy, as the Amerindian ones. And for the amerindian ones, we have two possibilities : 1)A legacy from historical colonization that is attested and that is enough to justify such change. 2)A possible solutrean settlement that is not proven yet.
So for now, without discovery that could infirm or confirm the second hypothesis, by applying simple logic, by retiring from this all the non necessary things (I'm sure that even if it's not an universal tool, the Occam's Razor can appply here), 1) is enough for now.
If this is so, then we should have found all possible shapes all other the world. But that is not so. Certain cultures used certain shapes. If you find artifacts of the same shape in different areas than it has to be the same culture. This is simple logic. And it is unrealistic to assume that a culture suddenly uses a different shape without outside influence (= another culture using that shape).
Pyramids are a common shape, are you suggesting that is coming from the same culture?
Again, there is no an infinite way to shape objects and it's quite common to see two cultures, without contact, using it.
Compass, Print, Rudder in Europe and China, are the most known exemple of how two distinct cultures can join themselves. Suggesting that ONE object can only came from ONE culture except influence is not just unreealistic, it's historically wrong.
Even agriculture was discovered independently on the two continents, damnit!
So yes, Amerindian could have perfectly shaped differently their artifacts by discovering ways of perfoming these. And again, there is no 100 way to do it.
Actually, you can find the same features in subsharian africa and Australia.
Unless you're suggesting that solutreen settled these places, you have to admit that yes, same features can be discovered independently by different cultures.
If not, i'm sorry to say so, but you'll have many issues understanding what historical artifacts can learn about pre-history and history.
Sadly many still think that all Native Americans had immigrated from Sibiria. And they ignore findings which cannot be explained that way.
To make it simple, nobody knows for sure if there was only a Siberia->Alaska migration or not. If the Clovis hypothesis is clearly to be replaced, it's not meaning that the traditionnal explanation is false.
The solutrean hypothesis pose many issues again : parietal art and relative limitation of how making performing prehistoric tools.
It's not infirming this hypothesis, but it's not at all confirming it. Only a possible new discovery could do it.