My explanation is that they brought many diseases with them from Africa and Spain and that alone killed many native Americans by millions and they also had them overworked and beatin which killed them off too, also they were killed and used to work in mines and they were to convert to Catholicism or be killed. There were barely any good effects like the exchange of goods and introduction to things like horses and potatoes.
hopefully this helps you and if it does mark brainlest pls it really helps. ;)
