AA does not need to operate ORD-TYO nonstop service on its own metal with AA's partner JL already serving TYO nonstop from ORD along with AA being able to connect passengers onto JL's ORD-TYO nonstop flights from other Eastern U.S. destinations.
While AA hasn't yet started SEA-PVG nonstop service due to the COVID-19 pandemic, AA has plans to serve PVG nonstop from SEA due to the AA-AS partnership along with the connecting feed that AA would be getting onto SEA-PVG from AS flights to SEA and AA CLT/ORD/LAX/MIA/PHL/PHX-SEA flights.
AA's partner JL also offers connections to PEK, SHA, and PVG from ORD and LAX through TYO.
No one was arguing that AA needed to operate ORD-TYO butt he fact that that AA could not make the route work, even with a 787-8 illustrates the challenges AA has had with TPAC. The role of ORD in the AA network is very different now than it was pre-merger, but it remains a large one and yes, obviously, JL serves the market but still...
AA successfully moved LAX-PVG to SEA, but hasn't started the route yet, because of the pandemic, of course. Obviously, AA will benefit from AS feed at SEA for this route, but it remains to be seen just how successful it will be regardless. Absent AS, AA wouldn't have a shot and I am not sure it will pull as much traffic from its US hubs through SEA to PVG when the route does get up an running as much as it will pull from AS's SEA hub.
I’d argue that intense competition is the primary reason for AA’s struggles in Asia. In ORD they competed with Asia-powerhouse United and its partners plus Hainan and China Eastern, and LAX was even more of a bloodbath.
SEA is probably their best option, yes the AA connecting traffic will be limited BUT AA will route anything east of the Rockies through DFW, where it has been successful. West of the Rockies AS has a pretty good network and can feed that traffic in SEA. There will still be competition from DL but Delta is not exactly an Asia powerhouse either.
AA has not been able to make Asia work for decades. It's point-of-sale originating in Asia isn't great, even though it has strong partners in CX and JL. AA looked at Pan Am's TPAC route network in 1986 and opted to pass on buying it. Bob Crandall thought the network would be costly to operate and sustain and AA at the time, didn't have the fleet to make most of it work. It has tried several Japan routes outside of Tokyo once or twice from DFW, and they have not worked out. To China, AA has yet to develop much of a expanded partnership with China Southern, a move that was hindered (and continues to be) by the pandemic. JL is a strong partner but connections over TYO really aren't as valuable as they once were, as most of Asia's top business destinations are reached nonstop from somewhere in the US. AA arguably missed the boat on Asia, which, had they moved on it in 1986, would have landed them with a commanding presence similar to what they have in Latin America which emerged from 1990 onward with the acquisition of EA's route network to Latin America.
SEA is yes, their best option, and having AS as a partner in OW helps a lot. DL's TPAC route network is a distant second to UA's but has the legs of the old NW route network and sales strategy in the region.
The future of AA on TPAC will look something like this: DFW to China, Japan, Hong Kong, Seoul, and perhaps one additional Asian destination, SEA for PVG, HND, perhaps SIN, and who knows what will happen with BLR, LAX for Australia, New Zealand, and Japan.