Manifest Destiny was basically the belief that the US was destined to span coast to coast, regardless of the Native Americans or Mexicans that stood in the way. It’s a very imperial mindset.
The moment we sit down and start singing Kumbayah some neighbour will take his chances to sweep us up. If ever we were to manage to tame the entire human race into singing Kumbayah we'd be taken over by a fleet of flying saucers, sapient gorillas or just rebooted because the simulation entered a state of deadlock. It isn't just humans either, strife and conquest are a fact of life from the most primitive life forms to homo sapiens and everything in between.
To that point I think indigenous societies were doing just fine. It wasn't a fact of life to lose a language or entire culture within a generation before settlers arrived. You didn't inherit a position of serfdom. Property rights weren't a thing. Women could get divorces and had political authority. In many tribes non-binary genders were accepted or even the norm. Tribal warfare did not kill millions indiscriminately.
Entropy may be a fact of life, you don't have to contribute to it more than necessary. If we are already warring with things like flatworms and COVID maybe warring with each other is counterproductive and a "dark pattern" to be worked on. Food for thought
In other words, Rousseau was wrong, the savages have the same vices and the same virtues as we have. Wake up from your dream of the perfect past which came to an end when the evil white man came to conquer and welcome to the real world. Read some real history instead of Howard Zinn and Nikole Hannah-Jones, have a look into the different forms of slavery as practised by those "indigenous societies", read up on the Aztec's own claim of sacrificing 40.000 people over a 4-day period for the re-consecratino of the Templo Mayor in Tenochtitlan or the 50.000 to 200.000 (historians quibble over the actual number) who were sacrificed every year. Heading into the temple complex your eyes would be drawn to the steep double staircase on the Grand Templo Mayor. A trail of blood leads to the impressive top of the temple, a flat working area where the captives or the occasional volunteers were brought to be sacrificed where most of the city could see. Most of the temple-top sacrifices involved cutting through the abdomen and diaphragm to rip out a still-beating heart. Not to paint them with a black brush, just to realise those "indigenous societies" were just as "guilty" of "sin" as all others.
Wake up.
It's also kind of gross that westerners need to equate every state with their specific settler-colonial ones. All of those "colonialist languages" co-existed for hundreds of years and were only endangered by the introduction of European settlers. The wholesale liquidation of entire cultures was something uniquely western, and as a consequence the only languages I have left to describe the crime are those belonging to the criminals that did it. In 100 years the Aztecs did not do what the Spanish did in a decade. I'm sure you'll say the Aztecs simply lacked the means, but then you're comparing them to an actual settler-colonial empire.
You say Aztecs were an unpleasant bunch and that's why other tribes helped the Spanish, but as I remember it the conquistadores were welcomed as Gods in Tenochtitlán. Doesn't seem like a very unpleasant welcome, the reward for which was razing the city and killing millions. Seems to me like the other tribes might have helped the Spanish because they knew which way the wind was blowing? Or maybe they also viewed them as gods. Can you ask them how they felt about the Spanish once the Aztecs were gone and the conquistadores enslaved everyone, mutilating people for not mining enough silver?
It’s kind of telling why people need the victims of genocide to have somehow “earned” it, either from being “weaker” or “just as bad”. I choose to not minimize the slaughter of around 100 million indigenous Americans in the "New World". There is no justification for it nor was there precedent.
"As for what we were like before we met you, I no longer care. No periods of time over which my ancestors held sway, no documentation of complex civilizations, is any comfort to me. Even if I really came from people who were living like monkeys in trees, it was better to be that than what happened to me, what I became after I met you." — Jamaica Kincaid