Native peoples of America had no immunity to the diseases that European explorers and colonists brought with them. Diseases such as smallpox, influenza, measles, and even chicken pox proved deadly to American Indians. Europeans were used to these diseases, but Indian people had no resistance to them.
The Framers wanted the nation to be a democracy where the people controlled their government rather than the government controlling the people. So, they allowed the Constitution to be amended but only by a majority of states to ensure that the people wanted a Constitutional Convention.
Guaranteed rights to free slaves
basically said if you were born in the US you're a citizen race didn't matter anymore