I think that it would have been wise to try to reach Aeroplan/Air Canada while you were at PEK, but hindsight is always 20:20.
Since this was a single award ticket for travel to the United States, I would file a complaint with the U.S. Department of Transportation against Air Canada (which I assume was the issuing airline). While the DOT cannot order an airline to compensate you, it can bring an enforcement proceeding against an airline if DOT perceives that the airline is not acting appropriately if they've violated DOT consumer-protection rules. DOT complaint information here:
https://www.transportation.gov/airco...umer-complaint