My limited reading of the subject has not produced any satisfactory answer.
Yes, we do in fact.
The German campaign in the south Atlantic started in 1940, with associated losses of Allied shipping. This route was important for the British especially, as it offered a route to the east including India and Burma.
It appears that in 1941, the United States perceived this as a threat to it's shipping and war support, which is interesting because the data seems to show no US ships sunk anywhere near the south or mid Atlantic!. As well, the Dictatorship of Brazil was officially neutral, but was favorable to the dictatorships in Germany and Italy with their strong nationalist messages. This meant that many times a U Boat would hide in Brazilian waters while waiting for an opportunity to strike back into the Caribbean or Atlantic. Due to this perceived strategic threat, the US negotiated a treaty with the ruling faction in Brazil for the placement of US forces in Brazil, and the associated usage of Brazilian assets to hunt and kill Axis subs. This allegiance begins in the second half of 1941, with the first US Naval and Air Forces based at Recife and other Brazilian bases by December 1941. Subsequently, Nazi Germany and it's Axis partner Italy began attacks on all Brazilian ships, found anywhere. The first Axis subs in Brazilian waters, with the intent of conducting operations against the Brazilians, appear in April 1942.
Remember that Brazil is still neutral at this time, and is simply attacking subs in its waters. Mid august 1942 changes that: U-507 enters Brazilian waters and goes on a rampage of sinking, many of which were conducted without first verifying the flag/type of shipping being attacked. Instead, the sunken boats were simply silhouettes along a well lit coast. This accounted for 7 ships at 18,000 tons total with ~ 600 dead neutral civilians. Because of this, Brazil officially entered the war on 22 August 1942. This single attack likely changed the course of the war in South America: Many of the proto-dictatorships there were "Neutral/Favorable" to Nazi Germany and Fascist Italy; but the assault by U-507 changed that.
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