Dr Richard Johnson, Lecturer in US Politics and Policy has written an opinion piece for The Conversation in which he explores why so many US presidents like to say they're Irish. He writes: "Biden’s references to his Irish ancestry do not distinguish him from other US presidents. With Donald Trump being the exception, nearly every president of the last half-century has identified as “Irish”, even when the evidence of such a link has been tenuous. Bill Clinton, for example, claimed to have Irish roots, but there is scant record to link him with Irish ancestors."
This was as covered in The Conversation