South American Ingredient Substitutions and Equivalencies

This is not meant to be exhaustive nor definitive, I've just tried to give information in a format that I hope will be useful for others in my position who are used to standard American ingredients...if you have any tips or clarifications please send them my way!

Sugars

Demarera sugar
azúcar blanca: granulated sugar, often more coarse than American sugar (in Brazil it tends to be about the same coarseness as the American version)

azúcar integral (Argentina): ground panela; it looks similar to American brown sugar but will often throw off the texture and taste of baked goods. Can sometimes be found in las dieteticas; it's produced in Tucuman.

azúcar morena (Colombia): similar to demarera and turbinado sugar (like Sugar in the Raw), works as a replacement for white sugar though it is coarser and has a more caramel-y flavor

azúcar negra (Argentina): generally white sugar with colorant added, somewhat similar to brown sugar

azúcar rubia (Argentina): light brown sugar, very similar to American light brown sugar

Brazilian muscovado sugar
demarera (Brazil): similar to azúcar morena and turbinado sugar (like Sugar in the Raw), often works as a replacement for white sugar though it is coarser and has a more caramel-y flavor (which I sometimes really like) 

mascavo (Brazil): muscovado sugar; similar to American brown sugar with a slightly stronger sugar cane taste that varies between brands

panela (Colombia): extremely similar to rapadura, not a good substitute for American brown sugar; has a very strong taste and is much less sweet that white sugar. You need to grate it in order to use it-- it's basically a hard block of boiled down cane sugar.
 
rapadura (Brazil): extremely similar to panela, not a good substitute for American brown sugar

Brazilian rapadura sugar
Additional notes:
-Molasses is sold as melado or miel de caña and is generally lighter than the American version. Boiling water with a high proportion of panela/rapadura will give you a very similar product.
-Brazilian unprocessed sugars tend to taste more like raw sugar cane than Colombian versions, and they often have a greener tinge.
-Powdered sugar is known as azúcar impalpable in Argentina, azúcar pulverizada in Colombia, and açúcar de confeitar in Brazil.


Grains

-Rolled and steel-cut oats are extremely hard to find in Argentina and Colombia. Avena gruesa, avena fina and avena instantánea are all versions of what Americans consider quick oats. Rolled oats can be found in Brazil as aveia em flocos grossos.
-Wheat berries and farro are both sold as trigo entero; you´re more likely to come across farro in Argentina and Colombia and wheat berries in Brazil.
-Barley is cebada (Spanish) or cevada (Portuguese)
-Polenta can be found as polenta in Argentina and cuchuco in Colombia; in Argentina the most commonly sold kind is instant, which isn't a great substitute for American cornmeal. If you can find non-instant polenta (sometimes sold in the bulk section), that works quite well for cornbread etc.


Flour

-All-purpose flour is labeled as tipo 000 in Argentina; unfortunately I have never seen unbleached all-purpose flour in the grocery stores. I have no scientific basis for saying this but I suspect that American flours have a higher protein content than Colombian and Argentinean ones-- sometimes I find I need much more flour in order for baked goods to reach proper consistency here. Harina leudante is self-rising flour.
-Whole wheat flour is called harina integral and varies greatly between country and between brands in terms of coarseness and bran content.