La Cosa Nostra is the Italian-American Mafia of the old United States.
Prior to the Sixth World, Italian immigrants to the United States were followed by members of criminal societies back in Italy. Who ended up establishing crime families in the United States which grew in wealth and power during the Prohibition Era in the 1920s from the bootleg liquor racket. They went on to form the National Syndicate and dominated organized crime in the United States for decades.
Though by the end of the 20th century they were being challenged by vicious nationwide prison gangs like the Mexican Mafia, in addition to a wide variety of smaller ethnic gangs in numerous cities (e.g. Irish, Jewish, Russian, Puerto Rican, Chinese, Vietnamese, Mexican, etc). The Cosa Nostra took advantage of the chaos which the return of magic caused, opening it's doors to all the ethnic mafias which it had been warring with in the past. Which resulted in the creation of a new multi-ethnic Mafia.
In the new North American Mafia, though it is a multi-ethnic and multi-racial mafia, the Italian-American crime families still continue to dominate. The great majority of the major crime families are of Italian descent. Controlling the Commission are the Five Families of New York City. It is also from within its ranks, that the Mafia experiences its main opposition to acceptance of the Awakened and metahumans. From Italian-American crime families such as the Five of New York City, the Mossino Family of New Orleans, the Ciarniello Family of Seattle, and the Morelli Family of Boston.
La Cosa Nostra was organized along the lines of the Sicilian Mafia. They were divided into families, who were ruled by Dons. These families were organized into regions (based on geographical areas around major cities), with each region ruled by a Capo (fem., Capa). The Capo leaders as a whole were called the Commissione.