FYI I live in an area with a large population of American Indians/Native Americans. While it’s most common to simply use the name of the particular tribe if your are identifying someone, “Indian” is the most common catchall term (and i think that recent polls show that a lot of American Indians/Native Americans disfavor the term “Native American).

I get that if you’re not in an area where American Indians comprise a large portion of the population (which is most of the world) that Indian may be more likely to refer to South Asian Indian, so no quibbles with your point in that regard. But just wanted to clarify that “Indian” is not an unusual way to refer to American Indians/Native Americans as a catchall when a particular tribal name is not used.