I am an Indian citizen flying AirIndia from Ahmedabad to Delhi, and after a three hour layover at Delhi airport, I fly to the US (on a student visa). Is this time sufficient to get through immigration, etc? This is part of a round-trip (US-India-US) that I booked on United/AirIndia, and I also have travel insurance.
Yes, it would be enough. Both AirIndia and United fly from T3, so you don't need to change terminals. You'd however would need to exit the airside and go through passport control and security again, because domestic and international departure areas are different. Passport control line might be long, but there's still plenty of time. And AirIndia seem to be very punctual nowadays - had a bunch of domestic flights in India this year, and they were always on time.