OP mentioned stopover...not sure if admissibility to Canada would need to be proven at initial departure. If this was a connection, OP would not be able to check in or board India-US flight without proof. For a stopover, not to mention one where the segment to Canada isn't for 5 months, and assuming OP is not US/Canada citizen, would they really require a valid ETA to board India-US flight (asking as I honestly have no idea).

Also, not sure if this is still the case, but I believe there used to be a rule on ex-India tickets where you could cancel and get a refund if you are not given the appropriate visa to travel to destination, though that would be murky here at best if OP had documents to travel to US but not to Canada.