I'm not prepared to split hairs over percentages that still exist. South American was also subjected to the Columbian Exchange of diseases, and populations were annihilated. What you see as "native populations" of South America today are really hybrid descendents of natives, Europeans, Arabs, and Africans:
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Perhaps some indigenous tribes were spared because the jungle environment of South America meant that contact with such tribes could be delayed until the diseases were brought under control, but on the whole, they were not spared where contact was made.
The reason why South Americans don't give themselves the lash over the same genocide for which they hold today's Americans responsible is that the Third World has exempted itself from any blame. The First World is always evil, and the Third World is always an innocent victim, remember? South America is so conditioned to accept this "truth," that it will overlook any number of obvious and bizarre contradictions to that "truth," such as how its population came to look the way it looks, or why there is such an extreme disparity between the rich and the poor in Latin America. It's the same mentality that allowed Brazil's Lula, who is married to a blue-eyed blonde, to rail against "white people with blue eyes" for causing the financial crisis. Of course, since he's South American, it's impossible for him to be racist.
Please, leave it alone. If you delve too deeply, you might learn about the deep hypocrisy and moral degradation of South America that resulted from its own involvement in the slave trade and enforcement of class systems. Who would you blame for all of your problems then?