David Jacobson is vice-chair, BMO Financial Group, and the former United States ambassador to Canada

From 2009 until 2013, I was entrusted with the responsibility of nurturing and sustaining one of the most important advantages the United States has anywhere in the world: our relationship with Canada. I saw first-hand how we make things together. How we defend the security of North America together. How we partner around the world to foster the values we share.

In speeches, I often used to quote president John Kennedy. Words which are literally carved into the granite wall of the U.S. embassy in Ottawa, reminding us that: “Geography has made us neighbors. History has made us friends. Economics has made us partners. And necessity has made us allies. Those whom nature hath so joined together, let no man put asunder.”

Story continues below advertisement

As I have watched events unfold over the past several months, and most particularly over this past weekend, I fear we are putting it asunder.

While I loved my time in Canada and I have made so many Canadian friends, I am an American. That’s where my allegiance lies. And from the American perspective – let alone the Canadian – undoing the North American free-trade agreement, imposing harsh tariffs and shouting names across the border are harming the United States’s interests in so many ways.

First the obvious. While economists can argue about whether NAFTA supports eight or nine or 12 million jobs in the U.S., it is clearly enormously beneficial to our economy and to the jobs Americans depend on. That’s why most representatives of the United States business community, from the U.S. Chamber of Commerce (on whose board I sit), the Business Roundtable and the overwhelming majority of American CEOs support NAFTA with some modernization, oppose tariffs and stand against the possibility of a trade war.

We need to remember that trade is not about counting up surpluses and deficits. While some argue that trade is a zero-sum game and that we need to win at the expense of others, that’s not true. Free trade increases efficiencies, reduces costs and strengthens competitiveness for everyone. If we cancel NAFTA and end up with reduced growth, America won’t have won anything. We will all lose.

But the economic impact on the United States is not the only – or the most important – casualty of our actions. As a friend colourfully reminded me the other day, when it comes to dealing with an integrated world, “the knee bone’s connected to the thigh bone.” We can’t get much done without friends and allies.

In my own experience, on several occasions I went to the Government of Canada with a request from Washington that might not have been at the top of their list. Nonetheless, Canada would usually support the United States, if for no other reason than because it was important to us. It went the other way as well. I suspect the next such request from the United States might not be so well received.

Finally, suggesting that Canada (or for that matter Britain, France or several other countries) amounts to a national security threat to the United States undermines our credibility in the world as well as our ability to call on our allies when we need them most.

Story continues below advertisement

In my time as ambassador, I went to Afghanistan and visited Canadian and American troops who were fighting together. I attended a ramp ceremony in Kandahar when a Canadian soldier was put on a plane for the final ride home in a flag-draped coffin. I visited military cemeteries in Europe where Canadians and Americans are buried side-by-side. Saying that countries who did so much to fight for our shared values are security threats to the United States undermines our ability to seek help when we need it.

I hope the trend of the last several months is reversed. I hope the words of president Kennedy on the wall of the U.S. embassy in Ottawa still have meaning.