While different legal and political systems must be factors in the differing developments of the Americas, there are geographical features that will remain the same no matter who is in charge:
The coast of Brazil is mostly cliffs - beautiful to look at but a bugger for transportation from the interior to the coastal cities or for export to the rest of the world, so this seems to be a challenging territory to run in a way that avoids poverty or extreme inequality (and the social and political difficulties that may arise from that). If it were not all one country from North to South, it could make a difference - a smaller country that centres around what is Sao Paolo OTL could maybe be a significant economic player.
The area that is OTL United States has enormous agricultural potential - more than the rest of the world, probably - whoever is in charge. A historical change that again sees this territory divided, developing under the control of competing countries of comparable power, could block some of this potential - provided no single country had control over the whole river network, I think.
Argentina is also lucky in its geography, agriculturally speaking - this seems to me the easiest part of South America to imagine developing in a wealthy, stable way.
Another question would also be whether these areas would be put to different use as colonies if taken by different countries, and I'm not so sure they would - for instance, if the English, French or Dutch come upon silver in South America they will probably still want to import slaves to get it - again because the geography - whether you're in a flat plain, mountains, or jungle - determines their economic use as colonies.