It's pretty normal to talk and write about subjects with which you are familiar.
Most people are comfortable, even enjoy, enlightening others about what they do and how it's done.
It makes sense to use your knowledge, your connections, all the hard work of research, to write about an area that is of continuing interest to yourself. Sherman Alexie is an award winning author, having received the 1994 Lila Wallace-Reader's Digest Writers' Award, the Before Columbus Foundation's American Book Award, named one of Granta's Best of the Young American Novelists, and high praise from The New York Times Book Review, The Boston Globe, The Nation, Library Journal, Chicago Tribune, and other well known reviewers of books. However, you don't have to be born a Native American to write about them, as attested to by prolific author Tony Hillerman. He studied at an Indian boarding school, yet he isn't a Native American. His college work was all at western universities and he has worked in journalism in Texas, Oklahoma and New Mexico.