As for how the US would benefit?? IMO it would strengthen Mexico's economy and make for better paying jobs/more $$ for them, and save us billions of dollars that we spend on immigration related expenses and crime/border patrol.
Here's a copy/paste of the facts....
[edit] History of the North American Union concept
Main articles: Independent Task Force on North America and Security and Prosperity Partnership of North America
In the 20th century the first well-known proposal for a form of North American unification was the North American technate proposed by Technocracy Incorporated in their Technocracy Study Course published first in 1934. The technate would include not only Canada, the U.S., and Mexico, but also Central America, the Caribbean, Greenland, and parts of South America. A technate governing North America remains an objective of the organization.[6]
Most mainstream interest in a North American Union has focused on the Security and Prosperity Partnership of North America (SPP) which finds its origins in proposals for increasing integration in the NAFTA trade bloc during President Bush's first term. Such ideas were commonly called proposals for a NAFTA plus.[7] Former President Vicente Fox of Mexico proposed such an agreement including a NAFTA energy policy, a security NAFTA policy, an advance in financial institutions interchanged,[8] and according to other reports a common market, development fund, migration agreement and new institutions.[9] Fox said such an agreement would take the U.S. and Mexico to a "further integration" and eventually seeking a "convergence" of their economies allowing them to "erase that border".[10]
The attacks of September 11, 2001 turned the focus of integration towards American concerns about security and away from Mexican concerns about immigration and open borders.[11] When the SPP was formed in 2005, a migration agreement was not mentioned focusing instead on synchronizing regulatory policy, reducing congestion at the border, and rationalizing external tariffs. The SPP, however, did include Canadian proposals for reducing congestion at the border.[7]
Prior to the formation of the SPP the Independent Task Force on North America, a project organized by the Council on Foreign Relations (U.S.), the Canadian Council of Chief Executives, and the Mexican Council on Foreign Relations, launched in October 2004, published two documents calling for greater integration between the three countries: Trinational Call for a North American Economic and Security Community by 2010 (March 2005) and its final report Building a North American Community[12] (May 2005).
Their final report, which has been described as "an academic exercise with pretensions of reaching policymakers,"[11] proposed increased international cooperation between the nations of Canada, the United States, and Mexico, similar in some respects to that of the European Community that preceded the European Union. The report called for "establishment by 2010 of a North American economic and security community, the boundaries of which would be defined by a common external tariff and an outer security perimeter." No recommendation was made for a common currency or a supranational institution like the European Union. The report said that a North American Community should not rely on "grand schemes of confederation or union".[12]
In reference to the March 2005 summit in Waco, Texas that established the SPP, the task force's final report stated, "We welcome this important development and offer this report to add urgency and specific recommendations to strengthen their efforts."[13] These specific recommendations include developing a North American customs union, common market, investment fund, energy strategy, set of regulatory standards, security perimeter, border pass, and advisory council, among other common goals.
The formation of the SPP, the reports from the Independent Task Force, and comments from Vicente Fox were cited as evidence for a planned North American Union. Theories about an ongoing plan are predominant on the Internet, especially among bloggers and other writers.[1] Jerome Corsi's columns on WorldNetDaily and Human Events, as well as his best-selling book The Late Great U.S.A.: The Coming Merger With Mexico and Canada, formed the core of NAU conspiracy theories.[5] Corsi himself is often referred to as the leader of the anti-North American Union movement.[