There's very real potential to step into the space vacated by Thomas Cook if we're talking a commitment to a based fleet of A321Neos to secondary US cities on a semi-seasonal basis carrying Brits to the US. Aer Lingus have only ever flown long haul east once to Dubai and that wasn't huge success and ended when Emirate came along or just prior. And the A330 to the Caribbean is a good use of capacity and it's a well know brand so why not?
Going East is going head to head with the ME3 with huge connecting opportunities to many more destinations, whereas the US is now relatively underserved from MAN.
It will kick off in Ireland if and when SNN-US restarts and "Manchester won't give Shannon their aircraft back" and cries of "theft". It's not ALL commercial, politics will get involved but they do have more long haul aircraft than needed by some way for 2021 and probs 2022.