I'm sure that many in the US will use it as further proof of the anti-Americanism of Latin America or something like that. In reality, though, it makes perfect sense. The Latin American countries have a commonality that doesn't include the US and Canada.
I am not so happy about the announcement that the new organization will support Argentina's claim to the Falklands. I know it's a major sticking point for Argentina, but it's a settled issue and the residents have long supported the status quo.