The obvious and most likely explanation and conclusion... They were slaughtered by the savages.
Indigenous tribes in North America were violent bloodthirsty savages. They fought and killed each other and when the Europeans arrived, they were just another tribe to be dealt with. So they fought and killed Europeans until they figured it out... The Europeans had better weapons and didn’t stop coming... So the Europeans then became the most dominant tribe of savages on the land. Now the middle eastern tribes are trying their best to unseat the European tribes.
They weren’t any more or any less bloodthirsty that the settlers, and different nations had different languages, different cultures and traditions, vastly different behavioral patterns, from authoritarian to egalitarian, matriarchal and patriarchal, warlike and pacifistic.