In Britain we'd probably go with Native American in a formal context, American Indian might be used but probably isn't as common anymore I'd say, Red Indian wou

In Britain we'd probably go with Native American in a formal context, American Indian might be used but probably isn't as common anymore I'd say, Red Indian would be understood as well but it's a bit dated, I assume that would be considered an offensive term in the US though. So while we use/understand the term (American) Indians, Indian by itself would be considered to refer to people from India.