Reliable sources have said that some American Airlines have told the CAA that Cork's catchment area is too small to support a transatlantic service. It could be viable if there was greater recognition of the Cork Brand name in the U.S. But the reality is that Killarney and Blarney are better known in the United States than Cork.
Maybe Cork Airport could be marketed as Blarney International in the U.S. After all it's only six miles south of the Blarney stone and the planes even fly over it on finals to 17!