AA to Japan is really hard to find, if only because so many of their west coast flights are JL codeshares. I think your only AA-metal option is from Los Angeles, so there's not going to be much availability on that one single route even at the best of times. Maybe a little better if you start from further east, but I don't think that SEA-JFK-NRT (for example) is a valid award routing.
Korean's another option for AS miles but they've got a ton of blackout dates. Not easy to work with.