To most people it sounds kooky, especially when listening to some of the people explaining it.
People shouldn't talk about it like, "NAFTA is gunna to take away teh U.S. sovereignties in 2010 and mak3s it intoa corporate spurestate wif de amero!"
Fact is, NAFTA was just the first step in a very long process that will likely take decades. Right now it's just an agreement to break down trade barriers. With the SPP it's moving towards eliminating immigration restrictions and creating continental standards for all products.
It's also taking steps towards a continental-wide domestic security mechanism to go after terrorism, drug smuggling, human trafficking, and other international crimes.
All of it generally seems reasonable and not sinister and, for the most part it is. I myself would agree with a lot of these ideas as well as an international highway system connecting Mexico, Canada, and the United States.
However, just like in the EU, this is just how they spirit in larger changes and justify them. Eventually dealing with domestic security is going to involve protection from foreign threats of a military nature. So there's going be a NADA or North American Defense Agreement. Something of this nature was already proposed in a previous session of Congress.
Also after a while dealing with international crimes and insuring fairness in trade will lead to calls for some common legal mechanism and a court above national courts able to override national law, including national constitutions in order to maintain a consistent continental-wide legal system.
Eventually a common currency will be brought in simply as a way of further integrating the economies in the continent, however it will likely start by having all the currencies fixed to each other. That's a long ways off, though.
Here's an interesting way of looking at the economic side:
http://en.wikipedia.org/wiki/Economic_integration
Right now we're in the second stage of integration but are moving towards the third and fourth stages with the SPP. After that or during this you can expect the fixing of currencies to each other so as to make it easier to usher in a common currency. That would be the fifth stage of integration and eventually our economies will be fully integrated in the final stage.
