I have heard quite a few people here complaining against any political organisation that would look like the European Union, but applied to North America. Since no name has ever been give to such hypothetical organisation, and "American Union" is somewhat applied to the U.S.A. anyway, I will use "American Alliance" (and anyway, it has a nice ring to it)

I'd say the U.S.A, the U.S.M, and the Canadian Federation would all benefit from such political reach between our countries.

1) Common Currency. seening number of trade there are between our three countries, we really should consider getting a common currency (The Amero?) with which we could trade without the risks of currency change. Right now, many industries in Canada are hurt because of a too-quickly rising dollars, and I know that the same thing was true about USA companies doing trade in Canada before.

2) Common economical policies. Even if our 3 countries have sometime different economical goals, it is in our best interest to work together to set a continent-wide policy, and not simply "Washingtown decides, and Ottawa & Mexico don't have any choice but to follow".

3) Some king of common citizenship (or at least, open work borders, like in the EU). Oh my god, I am hearing huge outcry from many people.. "Mexican would steal out job!" But listen to these few points:

3a) http://www.thebestpageintheuniverse.net/c.cgi?u=walmart
3b) If Mexicans were allowed to work in the U.S.A., it would be illegal for companies to offer them lower-than-legal wages. And I do mean absolutely illegal (make strict laws about it). If companies had not the "let's save money" reason to hire illegal aliens, then the only reason they would hire them, it's if they work harder. Go back to argument a)
c) Open economical borders with Mexico will actually, over time, rise the way of living in that country, making it less and less interesting for them to cross over your border. Just see east-european countries that were allowed in the EU, their GDP is growing at a very good pace, and their population is getting richer over time, makign their situation more and more acceptable.
d) You could add an amendment that "Legal Aliens' children born in the USA, but part of the AA, are not automaticly citizen of the USA". There, another of your problem solved, and no more crossing pregnant mothers.

4) Common flag. Naa, let's keep 3 cultural distinct countries. USA should remain USA, like France remained France.

Right now, I thing I have ran out of arguments, but I'm sure others will crop out