Here’s my theory: he grew up in America and his mom was of Italian-Irish decent. She became a low-budget actress and met Gusteau while performing in Paris. Her acting failed she moved with Lingunini to France to have a life with G but then they died.
What do you think Alfredo Linguini’s nationality is? He lives in France, he has an Italian name, he has and American accent, and he looks British or Irish with his red hair.