As far as I know there are no bassinets on American Airlines planes. I have never seen them AA neither on transcontinental nor on trans-Atlantic flights.

The "Our Planes" page on aa.com has links to the maps for both configurations of the 767-300. Neither shows bassinets.

If this doesn't satisfy, I would call AA and work your through the reservations agents to someone who knows for sure - Customer Relations as a last resort.