Why do people so racist towards me?

I am an east indian guy. I am from northern india(kashmir) and lighter skinned than most other indians. people at me school and everywhere always say things like "are u sure you're indian"? and some even go on to tell me I must be descendant of white people. Is it so hard to accept that Indian people look diverse and our skin tone ranges from light to dark? Honestly Americans are obsessed with race.