This is one of the most frequently asked questions on the sub, but one that comes from a misunderstanding about what happened to the indigenous peoples of the Americas. Simply put, while disease was the immediate cause of the 70-90% mortality rate you cited, that rate would have been much lower (and populations would have eventually recovered) if not for the dislocation, enslavement, war, violence and famine caused and exacerbated by European settlers. In other words, Native Americans didn't suddenly get wiped out by a disease; they were hit by disease at a time when they were structurally (and deliberately) weakened and unable to withstand it like a human population normally would. Since these conditions did not prevail in Europe, no mirror pandemics would ever have occurred. See this answer by /u/anthropology_nerd and the rest of the thread, which has some very good background on this.