Actually, ethnicity and nationality here very often coincide. There is a strong sense of "belonging" to the region you're born in (this may be the result of complete different traditions, languages and so on between relatively close places here).
I live in Rome, and I'm Roman. Some of my friend that live in Rome since they were 12 live in it, but they do not call themselves Roman. I've got parents from the nort Italy, but I'm not part of that culture, while my parents are.
Tradition cannot be carried over if you've never seen the land from where that tradition comes from, and even if you have italian heritage and you're proud of it, you cannot call yourself italian, because you're completly separated from that culture, tradition and people.
Just having parents that are part of a culture doesn't make you part of that culture too.