Let's be clear, decades ago a political decision was made to restrict transatlantic flights to Shannon and Dublin. Cork was not included (and the airport had practically no investment over the past few decades) because the powers that be decided it would be a threat to Shannon's future.
Now, in the 21st century, Shannon is able to survive without political interference. Cork still lacks the runway length (as opposed to Knock) to cater for the vast majority of long haul aircraft to do transatlantic services.
The population in Cork City & County is vastly greater than the Shannon region. Most of the Cork population and virtually all business travel to the US originates in Cork and connects through either Dublin, London or Amsterdam.
A small percentage do the 3 hour return road trip to Shannon.
When scheduled transatlantic services do operate from Cork, they will be successful as they currently are from Shannon. All airports in Ireland should be given the opportunity to compete for this business. The sooner open skies comes in and the less political interference in aviation, the better.