Why would AA want to do such a flight if they could?

1) If Air Canada can't make it work from one of their hubs (YVR), I don't see how AA could. (AC can do LAX-YVR-HND connections as well as AA.)

2) A YVR-HND flight doesn't exactly fit in AA's 5 cornerstone market strategy. A one-stop flight from a cornerstone (LAX) to a major market (Tokyo) that's well within non-stop range doesn't exactly count -- it would be the only such flight in AA's system, AFAIK*. I don't really see how a 1-stop to arrive in HND at a terrible time could trump a non-stop to NRT.

This seems to fall into the realm of crazy speculation.

*AA has had tag legs within destination countries in recent years for various reasons (GRU-GIG and LHR-BRU, IIRC), but never a stop within North America at a non-hub, for good reason.