> I often wonder why the national companies haven't managed to widely export these or produce them elsewhere

The reverse is true as well. Some popular soft drinks in the USA are unknown in Brazil -- such as root beer, Dr Pepper, and cream soda.[1]

I think guaraná would be a success in the US and root beer could be a success in Brazil too. My assumption is that nobody wants to spend the money to create the market in a new country unless they're going to have a monopoly for at least awhile. But nobody own the flavors of guaraná and root beer, or even those names. After you've spent all the money to educate the public, some established domestic company would swoop in and take the market away from you.

[1] http://brazilsense.com/index.php?title=Common_in_the_USA_and...