Flights will only be available to redeem with AA or BA (or any other partner) miles if they are available at the low level on AS. AS has three award tiers. My experience recently is that most flights are available at the middle level (20k miles each way for domestic US).

For a 1401-2100 mile flight like MCI-SEA, my understanding of the award chart is that it should be 10k AS miles in coach if it's available in low. AS now has varying prices for the "low" tier, which makes this a little more complicated, and I don't fully understand their pricing. However, if the continental US award costs more than 12,500 AS miles each way in coach, it's not low and won't be available on partners.