As of the arrival of Europeans in the Americas, out of the hundreds of groups of natives living here, only a handful were still (or had even ever been) civilized. The remainder were still stuck in , or had fallen back into, the stone, or at best, bronze ages. It is not a fault of their genes - it was simply the harsh reality of being too few on too large a land area and without the benefit of all the cultural changes that had swept across South Asia, North Africa and Europe a few thousand years ago, culminating in the Romano-Hellenic secular and Judeo-Christian religious underpinnings of Western Civilization. As for the few groups that were actually nation states, by the time the Euros encountered them, they were well past their peaks and were essentially failed states. The arrival of Europeans was the best thing that could ever happen to the Americas. The Europeans saved the Americas from slipping further into what would likely have been at least 1000 years of the darkest ages ever experienced by the fragments of a former civilization. History is most unfair - and, is always right.
Bear with me for a second here, if you will. Let's for a moment assume that alien life forms exist and at some future date they make peaceful contact with us.
As a result of that contact they provide to us a cheap, reliable, safe and efficient source of power, which weens us from the tit of hydrocarbon dependency. The down side is that a disease, carried by and unknown (or not harmful) to the aliens, wipes out 70% of the population, before immunities or a cure is discovered.
Would you then say that the arrival of the aliens was the best thing that ever happened to us?