Alot of Europe was against this type of thing until it was forced on them. Now they seem to like it. I don’t want it for America though because we would be taking on two poor countries. With Europe they were bigger and have many more richer countries as part of the entire EU. Some Eastern Block countries are going to Euro in 2008. The EU is going to be quite a competition that is for sure.
Look more closely at the EU. It was originally established as a trading bloc to offset the impact that the US had in Europe as a primary source of manufactured goods. Over time, as the EU became more gargantuan (and more oppressive in its rules) opposition began to develop.
The heart of the story, however rests with the EU Constitution that would have created the United States of Europe. The EU Constitution was shot down and is now considered dead. Too many European countries realized that they didn't want to give up their unique national identity to become a homogeneous part of the US of E.
A NAU would only benefit Mexico (up to a point) by propping up their currency and dragging down the value of both the American and Canadian dollars. It would also allow Mexico to wholesale export to the US and Canada the people who are presently sneaking into the US as illegals. There is no benefit to either the US or Canada to participate in the NAU other than centralizing power - a politicians wet dream (and a nightmare for the rest of us).