He's really no different then your typical American mutt, he likes to think he's special by claiming to be Italian, but millions of Americans also have had an ancestor from the Italian penisula as well, some more then others have managed to cling onto their heritage a little better, but for the most part generations of Americans have assimilated to be completely detached from the country that their ancestors may or may not have come from.
If Phil couldn't brag about that tiny slither of his ethnicity, then he'd feel more insecure about himself I think. We know how much he likes to parade about all his authentic family recipes and shit, it puts him on a pedestal to look down on people who aren't Italian, because it makes him feel superior about certain aspects of that culture that come from being Italian.