I tried it already:
It wasn’t one of my better games and I doubt it should be used as a guideline (think it was my third Global?)
I wouldn’t recommend it under the current True Neutral rules unless Germany or Japan seriously sends some loaded transports and a carrier group to contest S. America (and be willing to invest in a minor IC as well). It’s just too much bonus to the US with all those extra free infantry produced. Japan could send a loaded transport(s) to take Chile on J3 in conjunction with an attack on Pearl Harbor; if Germany is threatening a Sealion and the US is built heavily into the Europe theater, it might work. You could also try a combined assault with Germany attacking from Gibraltar on G3 to seize Brazil or Argentina while Japan invades Chile; if you combine both carrier groups together and both powers built minor ICs, it could tie up the US for quite a while. It will also be a huge drain on the Axis war effort too, for a measly 8 S. American IPCs, but it might be worth it if it takes the US out of the war for another 4-5 turns.