Prejudice against Mediterranean types was not just a matter of poor immigrants to the U.S. It was prevalent in England as well.
One of the oddest stereotypes that pops up often in older English mysteries is the way the dark-skinned Europeans - Italians, Spaniards, Greeks - are referred to in racialist terms that are similar to, sometimes identical with, the terms used for Asian Indians and blacks. They are even called niggers at times. Any reference to darkness of skin color or similar code is often enough to alert a careful reader that the person is the villain who will be exposed in the end.