This is quite a complex question. However, I would say that Sherman Alexie writes from a Native American perspective partially to highlight current situations in Native American communities which are a result of the complex history. In addition being Native American himself, his characters speak with an authenticity.
In other words, his works are tied to Native American history because his characters and the situations they find themselves in cannot be separated from the history of Native Americans. His characters are a mixture of native beliefs and a result of adapted and evolved beliefs due to the reservation system. These characters also react to situations they find themselves in with this mixture. In addition, the situations the characters are in are also a result of the history of Native Americans.
All of this compounds together to give the reader (hopefully) a better understanding of Native Americans in the US today.