In beginning to read John Dickie's definitive history on the Sicilian Mafia and its connection to the American version, I couldn't help but ask myself why it wasn't as prevalent in Latin American countries with a heavy influx of Italian immigrants leaving the "old country" at approximately the same time. I recognize that there is a fair amount of the Calabrian counterpart "'Ndrangheta", but why not the more infamous of Italian organized crime?
Italian-Americans were a much smaller minority in their adopted country than Italian-Argentines. (between 1861 and 1920 they were 59% of all immigrants to Argentina). One of the major factors behind the early success of "Black Hand" type extortion rackets (which evolved into the American Mafia) in the U.S. was an insular culture with little trust in police protection.
The other major factor would have been national Prohibition. This, more than anything, was what changed the American Mafia from the type of vultures that pick at any immigrant culture to the criminal institution it became (and still is, to a lesser extent).