Don Brunell, president of Washington's Chamber of Commerce, points out the futility of "Buy American" and his argument cannot be over-emphasised: "Protectionism doesn't make sense because manufacturers today are international. They build, process and assemble goods in many nations and sell products around the world."

"The most visible impact of a new round of protectionism would be seen in the water treatment equipment and pipe sector which, in 2008, was worth $10.18 billion. The water treatment facilities installed around the world have integrated parts from many countries.
If Americans exclude Canadian products from U.S. water treatment facilities and the "Buy Canada" language sticks, U.S. companies and their workers stand to lose $6.18 billion a year. Canadian companies would lose $4 billion if they are excluded from providing pipe and water systems to American government projects.
You didn't have to get an "A" in math to see who the real loser is in this equation."

The CEO of Campbell Soup provides yet another glimpse of just how interconnected the American and Canadian economy are:

"4,000 shipments of ingredients for Campbell Soup's products cross from our country into Canada each day and 3,500 come from Canada into the U.S. Some of the vegetables cross the border twice when ingredients from processing plants in both countries are mixed, packaged and distributed to retailers across the globe."

Those criss-crossing supply chains create jobs, wealth and prosperity on both sides of the border.  They exist partly because the United States and Canada share a long border, but primarily because of the trade policies that encourage neighbours to interact with each-other in productive ways.

Don Brunell claims that "unbundling that supply chain would have a catastrophic effect. Figuring out where to start would be overwhelming." 

He's absolutely right, yet that is in essence what Buy American, and the equally stupid policies enacted in other parts of the world that mimic it, threatens to do.