Brazil and Argentina had a huge number of Italian immigrants like the US and Canada had in the 20th century, but I never heard of the mafia taking root there outside of a few guys hiding out there, or a couple guys connected to the drug trade. I could be wrong though, but if I'm right, does anyone know why the mafia didn't take root in these countries? Could it have been the Italians that immigrated to Brazil and Argentina came from regions of Italy that had little or no mafia influence?

yes most of italians who settled to argentina came from central and nothern regions, the southerner were a minority there that's because they never formed rooted and big mafia groups there

South America has more Italian-based groups rather than Italian-Argentinian\Brazilian\Etc hybrid ones.

Due to the drug trade, and the Italian-style political curroption, all Italian groups are believed to be pretty active down there. Mostly Calabrians and Neapolitans.
Also a LOT of Italian fugitives have been captured while in South America (Venezuela, Brazil, Uruguay).

Here's the link to a post by Furio_from_Naples with maps taken from Mafia Export.

- As far as the Italian immigration is concern:

The Southern American culture was way more similar to the Italian one. The was no need of creating a ghetto, a\k\a "Little Italy", like it happened in the USA\CND\AUS or even Germany and Belgium.
Few Italian areas were established of course, but there was no need to, compared to the other countries listed above...there was less (way less) discrimination.

Language, way of life and even genetic features were more similar to the one of the many Italians, so assimilation happened right away.
I mean: imagine being an Italian immigrant of the early '900s, with strong mediterrean features, moving to, let's say, Kansas City...now THAT will be a cultural shock.
Now you're the same guy, but instead you're gone to Venezuela...still different from Italy...but not that different.

And yes, the large majority came from Northern\Central Italy. Not that this bunch had NO criminals...but no historic criminal organization.

Even today (words of four college mates of mine all from Argentina, all with Italian lastnames), very few people call themselves "Italian-Argentinian", simply because their ancestors integrated faster in the local society.
These four guys were AMAZED when I brought them around our area and they saw a local Italian folk feast...with 2nd\3rd\4th generation Italian-Americans celebrating their heritage.
They even told me that, back home, during the world cup GOD FORBID if you cheer for Italy...especially if you're in high school or college!

Compared to the USA\CND\AUS and many other European countries, Visas and citizenship were easier to get too.

This are my two cents.

yes luankuci is right most of italian groups there are italian-based that's because i said they never formed a permanent mafia structure like in the states or canada etc... sicilians are present too there in brazil and venezuela especially, leonardo badalamenti has a multimillionaire empire

Heres a dumb example of mine Francisco Cervelli catcher for the Yankees Italian/Spanish descent born in Venezuela. Haven't heard of his family having any Mafia connections.

A little off topic, South American women are hot.

If you read a book on Tomasso Bruscetta (major Sicilian Mafiosi) he spend a lot of time in South America and did some business there with the drug trade.

Cant believe Id forgotten that, Nicky. Good one.

There are plenty of cases of mobsters from around North America and mainland Italy being involved in the staples (drugs and money laundering) in South America, and in some pretty profitable rackets, but as m2w stated (who is right in this case) there were never enough criminally inclined Italians to form "homegrown" cells.

Having said that, more and more cases of millionaire mafiosi hiding out in Latin America are always coming to light, where their ill-gotten funds greased the right palms in local corruption to afford them virtual safehavens.

The Rizzuto's had massive interests in Venezuela, as did the Cauruana/C.untrera groups, though also in Brazil.

Leonardo Badalamenti (one of Don Tano's sons) was a good example, based in Venezuela he was involved in selling fraudulent securities to foreign banks and made millions.
On another note, his brother Vito is alleged by some sources to be hiding out in either Brazil or Australia.

Another recent example of mobsters with operations in Latin America would be Ndrina Vincenzo Roccisano, who was recently sentenced to 46 months for illegaly re-entering the US. Known as a major trafficker in the 80's, he is alleged to be one of the architects of the "barter system" between Ndrine and the cartels, where heroin from the Middle East is swapped for cocaine.