English and Germanic settlers in North America acted as what they really are, tribes bonded by race. Not as a Civilization.
They treated Indians the same way they treated Gauls, Scots and Irish.
Of course, the Founding Fathers were cultured and illustrated people, but settlers were barbaric immersed in aberrant religions.
Catholics, on the other side, behaved in a Roman way. First, "civilize" (convert) to dominate and explote savages. Mestizos (with Indians) and Indians were considered legally as subjects of the Crown with no tainted blood (Jew or Moorish). Of course, settlers committed many abuses and crimes, but at least Indians were formally protected by the law and the Church.