My bad. I too should have considered that the term "Indians" is ambiguous and should have looked up the reference book. Thought the title "Great Plains" was referring to plains including the Indo-Gangetic plain.
Is "East Indians" the commonly used name in the US for the people of India ? I've come across "Asian Indians".
"Indian" is the commonly used term for the people from India as far as I know. You don't very often see that cohort referred to by some other term.
Interesting question. My impression from afar (I live in Japan) is that “Asian Indians” and “East Indians” are both used but that just “Indians” is increasingly common, partly because of the growth in the number of people in the U.S. from India and partly because of the growing tendency in recent decades to avoid using “Indian” to refer to native Americans. Wikipedia has a long article on the latter issue:
https://en.wikipedia.org/wiki/Native_American_name_controver...