the word "mafia" refers specifically to Sicilians. here in Australia, however, we have The Honoured Society / 'Ndrangheta, who originate from Calabria in southern Italy. they're still mobsters. they were heavily involved in the Victoria Market Murders and the Melbourne Gangland Killings in order to take over the drug trade and have for several years been attempting to dabble in politics here. some of them are quite well-known, including possibly Mick Gatto, who is an extremely generous individual.

Well, they have actually at various times been quite successful. Outside of the Sicilian Mafia's extensive American reach the Camorra infamously set up shop in Aberdeen, Scotland under Antonio La Torre.

The third of the big Italian crime syndicates, the 'Ndrangheta (who these days are one of the biggest drug running syndicates on the planet) has extensive setups in Germany, South America, Canada, the UK and the US.

Part of the reason why the Camorra and 'Ndrangheta's expansion relative to the Sicilian Mafia is because of how all three are structured. The Mafia primarily consists of "Families", who may be blood related at the top but a good chunk of their soldato are not. In 'Ndrangheta the "family" (or 'Ndrina) is more often than not genuinely blood related. Many will even conduct arranged marriages with other 'Ndrina for increased power.

John Dickie, Professor of Italian Studies at UCL has a great pair of books on the differences between Italian crime groups and why some are more international than others. Mafia Brotherhoods focuses on the rise of Italian organised crime up until the end of WW2 and Mafia Republic from 1946 to the present day.

As a follow-on, can someone explain why (southern) Italians have such a propensity for the mob life?

First, Thanks for asking this question! I thought the same thing weeks ago but forgot to ask. Second, everyone is mentioning the ndrangheta but OP's question was in the context of first generation immigrants communities. The ndrangheta expansion is recent. The same way the mafia took over NYC, why didn't the take over in the same way in other first generation italian communities around the world.

The best way to answer your question is by seeing how the American Mafia was able to gain power, and that is through Prohibition. Before Prohibition, there were many ethnic gangs throughout America especially centered in cities with large immigrant populations. These gangs were relatively small though, especially compared to what the Mafia would grow into and the other organized crime rings throughout the world, ie Russian Mob, Yakuza and others.

Pre-prohibition, there was a mix of Italian, Irish and Jewish gangs all throughout NYC, and for the most part, they kept their activities contained to their own ethnic groups. One of the early rackets for Italian gangs was actually in eggplants, as a large portion of Italian dishes had eggplants used in them. Prohibition allowed for these small gangs to gain access to a large amount of capital at relatively small risk. It also helped to turn these gangs from small time hoods to more organized groups. It wasn't until Prohibition that the modern mafia was created. After Prohibition, the five families of New York, along with those in Buffalo and New Orleans and a couple other, had the capital and the organizational skills to be able to expand into other prosperous enterprises. They were able to use their larger and more well funded organizations to push Irish and Jewish gangs out of business.

I don't know how large other Italian organized crime throughout the world is, but a small part of the equation would probably be that those communities didn't have the opportunities afforded to them through Prohibition. The Bratva grew in size and influence because of the dissolution of the Soviet Union, the Yakuza grew because of the use of a large black market during the American occupation of Tokyo as well as the fact that they stole a lot of armaments at the end of the war from the Imperial Army and The Italian Mafia in America grew due to Prohibition.