feel free to paraphrase the words of other tribal leaders between 1870 and 1890 since they basically shared the same fate.
I can't write the speech for you; instead, as the other editors have done, I can give you some pointers on what needs to be in your speech. I hope you don't mind my giving you a personal example. My grandmother was a Cherokee. Somehow her ancestors escaped the Trail of Tears and managed to settle in Tennessee. She didn't grow up on a reservation but on a large, extended-family farm. When she was 18, she went to live with a newly divorced white man to help take care of his son. Eventually she married him, and they became my father's parents. When she married my grandfather, my Granny decided that she would live as a white woman. She refused to tell her children any stories she had heard growing up. Her father had been a healer, and she had learned to be a healer too. But when she became "white," she also became a Christian and began to think of Cherokee medicine as pagan. Her children, growing up in the pre-civil rights South, were happy to be considered white, and they weren't interested in their Native American roots. Her grandchildren, however, wanted to learn about their heritage, but she still refused to pass it on.
When she died, my grandmother took all of that knowledge and wisdom with her. It was more important to her to live in the white world, to have her children be white so they could be successful, and to put all of the old ways behind her. Perhaps if she had lived on a reservation or a larger Native American community, she may have felt differently about being Cherokee and might have held on to her roots. But she resigned herself to living in a world in which native people weren't welcome. I'm sure many Native Americans assimilated into society in the same way.
In order for you to write a speech from the Native Americans' perspective regarding their 'resignation' to the obvious state of their experience you need to put yourself in their 'shoes'. There are excellent primary sources documenting the disillusionment of Red Cloud, Crazy Horse, and Sitting Bull. You might also look into the Bureau of Indian Affairs a government agency that was responsible for administering U.S. policy towards Native Americans. Just analyzing these programs one can begin to imagine the disturbing realities Native Americans experienced which would ultimately bring about their feelings of impending doom.
To approach this type of assignment, you need to keep in mind who the Native Americans were treated once settlers from Europe came into the New World. This harsh and unfair treatment of Native Americans began when the first settlement was made. Native Americans were slaughtered and imprisoned and banished, forced to move from their homes in many cases. They were shuffled around and were treated horribly. Imagine if you were a native of a particular place and suddenly, your home was invaded by strange looking people who were trying to kill you! This was what the Native Americans faced. Many people do not realize how horribly they were treated. Eventually, they were forced onto reservations, where many live today. They are self-governed. I have always been quite ashamed of how our country has treated Native Americans.