‘Yet another “We’re such bastards...” movie where the noble savages are abused, exploited, murdered by the mean’ol military. ‘
That’s usually how you take over a country. It worked here.
This wasn't a country 'til the Europeans came over and made it one. Had it actually been a 'country' in those days, the result would have been far different because the locals would have united and at least made the conflict difficult (or have dissuaded the colonists from trying to take over so completely).