WHY THE ITALIAN ACCENTS OF ITALIAN-AMERICANS DIFFER SO MUCH. Nosowitz points out that Italian-Americans speak a variety of dialects. The reason is the timing of immigration. Most Italian immigrants (80% of them from southern Italy) came over during the period between 1861 and 1914 before the standard Italian language based on Tuscan had been imposed. The next generation, if they learned Italian at home, learned one of the many different dialects that the immigrants spoke.
One result of this immigration pattern is that when these children visit Italy, they speak an old-fashioned language, from 50 years earlier. Standard Italian changed greatly during those 50 years, and the generation in America missed the changes.