No, Americans didn't kill "100 million Native Americans", diseases did.
A popular meme or 'argument' that is hugely popular on social media goes like this : 'Americans slaughtered 100 million native Americans.'
First, it's nonsense to claim that there were 100 million native Americans living in north America. Up to 18 million native Americans were living in North America around the 17th century. On the whole, It is estimated that the population of Native people in the Americas was anything between tens of millions to over 100 million in pre Columbian times. In any case, the native population declined to less than six million by 1650 in South America. If you want to blame someone for the deaths of Native Americans, in south and north America, you should blame European settlers who brought with them the bubonic plague, chicken pox, pneumonic plague, cholera, diphtheria, influenza, measles, scarlet fever, smallpox, typhus, tuberculosis, and whooping cough.
The scope of the epidemics over the years was tremendous, killing possibly in excess of 90% of the population in the hardest hit areas, and creating possibly the greatest human catastrophe in history, far exceeding even the disaster of the Black Death of medieval Europe. With the influx of European settlers into North and South America, more native population were exposed, and were eradicated as a result. In fact It was the European germs that did most of the actual conquering of South and North America, as they decimated the local population and literally depopulated both South and North America out of their indigonous populations. These germs and diseases were already introduced to South America in 1492, with Columbus first voyage. They worked their way up from South America to North America and wrecked havocks. It's estimated that most of the local population that dies from contracting these diseases, tens and tens of millions, died during the 16th century and the beginning of the 17th. Historians suggest that if it wasn't for these pandemics sweeping allover the continent empires such as the Inca would have never fallen to the Spanish conquistadors.
Aztecs Dying of Smallpox, 16th Century.
It's important to note that the European settlers, or colonizers, had no idea of the devastating effect they had on the native population. Historical myths that they used their diseases as some sort of bio weapon against local native populations, as in giving them blankets or other toold infected with contagious diseases are just that, historical myths. However, this is in no way should be interpreted as a defence of Spanish, English, French and American colonists horrendous, brutal crimes and actual conquest against the indigenous local population of south and north America. Crimes which included enslavement, massacres, rape and plunder on an industrial scale, destruction of whole civilizations and way of life, and the uprooting and ethnic cleansing of whole populations and people. However it is important to remember who, or actually what, was responsible for the deaths of the overwhelming majority of the indigenous population in the Americas, were diseases, not people and certainly not Americans, or the USA. Bibliography - "Guns, Germs, and Steel." by Jared Diamond. "Born to Die: Disease and New World Conquest." by Noble David Cook. "1491: New Revelations of the Americas Before Columbus." by Charles C. Mann