ANDREW MALCOLM: Trump vows major changes to NAFTA. Good luck with that, sir.

The U.S. and Canada have the largest bilateral economic relationship in the world, along with the world’s longest undefended border, 5,524 miles. Imagine the costs of that wall.

They’re tied by vast electrical, financial, intelligence and law enforcement networks. Nearly $2 billion in trade flows across that border every single day. More trade transits the old bridge between Detroit and Windsor each year than flows between the U.S. and Japan.

Americans have $380 billion directly invested in Canada, while Canadians have about $260 billion investments down south. Exports of goods and services to Canada support about 1.7 million U.S. jobs. The U.S. trade deficit there narrowed to $11 billion last year.

Fully 40 percent of U.S. imported oil comes from Canada before the Keystone XL pipeline.

Canada is 10 percent larger than the United States and forms the only geographical buffer with Russia. Its politics are way more liberal than the U.S., but Canada has probably been our staunchest ally. On a per capita basis, in fact, Canadian families sacrificed more lives in Afghanistan than the U.S.

As for Mexico, exports there support around 1.2 million U.S. jobs. The exchange of goods and services last year totaled about $597 billion with Mexico earning a surplus of around $55 billion, compared to the $336 billion U.S. deficit with China in 2015.

Americans have about $92 billion in direct investments in Mexico. Mexicans have about $17 billion in the U.S.

Those numbers are yuge.