Originally Posted by Mike Okitch

http://www.answers.com/topic/american-currency-union

"Currency union in the Americas is a proposal supported by some economists, but it is an idea that is not likely to be enacted in the near future. The idea is based on the common European currency, the euro. The theoretical American currency is sometimes referred to as the amero."

Read this. Interesting read actually. But even with tons of countries in South America using the US dollar as the de facto currency, they would still need to comply with very strict rules in order to make this a viable currency that would be capable of replacing the US dollar and compete against the Euro. I doubt that South American countries would be in a position to do that anytime soon.