I was born and raised in the US. I speak English natively and fluently, with a US accent.

A few times, in face-to-face, oral conversation, US-born colleagues or strangers have said something that reveals they assume I am an immigrant. I always found this bewildering; can't they hear my accent? In one case, last year, someone (a white person with a US accent) heard me say I was American, and replied "But your accent" -- the first time I'd ever experienced someone just making up a perceived Indian accent in my speech.

Turns out this happens frequently. Linguists in the US published research about it as early as 1992, and replicated findings, including in the piece "Code Switch" mentions. (Thanks to The League of Nerds for the bibliography that led me to the research papers NPR was citing.) From Okim Kang & Donald Rubin's "Reverse Linguistic Stereotyping: Measuring the Effect of Listener Expectations on Speech Evaluation":

In [reverse linguistic stereotyping], the speaker's language pattern is not the trigger to stereotyping processes but rather their object. In RLS, attributions of a speaker's group membership cue distorted perceptions of that speaker's language style or proficiency. Thus, Rubin and colleagues (see review in Rubin, 2002) have repeatedly documented that when listeners mistakenly believe they are listening to a nonnative speaker of English (NNS), they report hearing highly accented speech, and their listening comprehension significantly declines.

Well, at least now I know. Probably a ton of people have made this assumption over the years and I just never knew. And it'll probably keep happening; it's not like I'm going to start waving my long-form birth certificate around at the beginning of every meeting, party, and presentation. Bleh. Yet another thing.