"During unification, the northern Italian powers decided that having a country that speaks about a dozen different languages would pose a bit of a challenge to their efforts, so they picked one and called it “Standard Italian” and made everyone learn it. The one that they picked was Tuscan, and they probably picked it because it was the language of Dante, the most famous Italian writer."

The article was specifically about how the New Jersey Italian American accent came to be, so including details about Southern Italian emigration to South America and the rest of Europe probably wasn't necessary.