The number went up to 98%, the highest I have ever heard, of the percentage of the New World population killed by European diseases. That seems impossibly high, even to me, who has claimed a number of over 90% for over a decade myself. The estimates of original population have been rising over the years as well, up as high as 100,000,000 between North and South America together. Thirty million used to be scoffed at, but is now becoming a common estimate. The two estimated increases go together. Most of the people making estimates until recently have been Americans and Canadians, and the population density of the previous natives was low. It was indeed lower than in Mexico and points south, with perhaps only 5M over the whole expanse. But it had also be greatly reduced by disease prior to the arrival of the Puritans, due to diseases picked up from traders, combined with opportunistic attacks on weakened tribes by other tribes.
The diseases went on before, wiping out natives before Europeans had come within a hundred miles of them in person.
It didn’t all stem from Columbus’s discovery. The English would have found land off the Grand Banks soon enough, and the Portuguese discovery of Brazil was also a foregone conclusion given their experimental forays off the coast of Africa. Whether it happened in 1000, 1500, or 1700 AD, there was going to be contact between peoples, one of which had far less resistance to the other’s diseases than the other. Something similar happened in reverse in Africa, where it was the Europeans who died off of the local diseases, and we unable to penetrate for generations. The native susceptibility to alcohol also has inevitability written all over it. That population was last sundered from Asia thousands of years before fermentation was discovered (possible Ukraine, possibly eastern Mediterranean).
Is there any plausible alt-history where contact was not a catastrophe for New World Natives? Germ theory was unknown, but even with strict sequestering, don’t the diseases have to get through? Even the noblest and best possible behavior by the colonisers might have made little difference. I can’t even construct a plausible fantasy of how it could have turned out well.