Northern Italians are indistinguishable from Swiss and Bavarians, mostly because they're literally the same alpine people. All European countries today encompass multiple white ethnic groups, and some are more mixed than others.
Naples was a Norman possession for a long time. Sicily had a Greek, and Arab colony and ruler at different points in history, sometimes all three at once. It's a simple question with a long answer, but mostly "Italian" or "French" or "Spanish" isn't actually very specific and are all fairly modern terms (if you consider 1200 years modern, which I do). Italy especially, is a very very recent political creation.
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