South America had been neglected since launch — decorative territory with no focus tree of its own. This Country Pack gives 
Brazil, Argentina, Chile, Paraguay and Uruguay a voice, with the pull between Axis and Allied alignment running through the whole region.
What New Content It Adds
Like any Country Pack, it doesn't touch the game's mechanics: all the value is in the nation content, concentrated in a region that used to be empty map filler.
Nations: Brazil and Its Neighbors
Brazil gets the lion's share: a broad tree with both authoritarian and democratic branches. Argentina, Chile, Paraguay and Uruguay get lighter but functional content, with nods to the real tensions of the period — Brazilian Getulism, nascent Peronism in Argentina — that give texture to games that used to feel generic and interchangeable. South America is one of the least-developed regions in strategy games from this period, so this pack fills a gap with barely any competition, in English, Spanish, or any other language.
Who Is This For?
Worth it if you want to play Brazil or enjoy poking around corners of the map nobody else bothers with. If your priority is the major powers, you can skip it without noticing the difference.