Over in Terramagne, you can see how this influences some of the main characters. Ham, as part of the Damask collective, has a Sicilian grandfather. So Ham has a very Italian-American flavor of expression.
The Marionettes as a Family have spread throughout much of Italy, and beyond, but their highest concentration remains in the southerly parts -- Sicilia, Calabria, Puglia, and so forth -- whose regional differences contribute to the cultural flavor. T-Italy is less assimiliated but more tolerant than local-Italy. It's more common for people to speak a regional dialect as their home language and keep Standard Italian for public or official discourse. I've caught a few instances of my Marionettes codeswitching not only between English and Italian, which they do a lot, but also into Sicilian, which they pretty much restrict to people they consider family. This little extra bit of flexibility is also why Italy has one of the more integrated soup cultures -- there are more than a few soups on the police force, mostly strongmen and speedsters -- and the Mob conflict is a periodic nuisance rather than a culture-wrecking disaster.