I did not know this, do you have a link for more information? How long before the flight do you need to do the test, 72 hours? Could you do one PCR test 2 or 3 days before to meet the Indian requirement, and an antigen test a few hours before the flight to satisfy the US requirement?

I could not find any information about a RT-PCR test requirement to exit India that is in addition to the destination countries test requirement. The only thing I found that was close was this https://www.airindia.in/images/pdf/G...om-India-1.pdf that says if your destination country requires a RT-PCR test, then it needs to have a QR code.