Cork is very, very unlikely for an Aer Lingus transatlantic service, but without the A321 it is definitely not happening.
My guesses are all from Dublin to
Dallas
Denver
Las Vegas
The first two are simply the largest US airports without a direct Irish service and also good for connections, whether American or United
The last because I reckon they know the level of Irish business through New York, Boston, Chicago and London and can see that it would work.