The customarily calm David MacNaughton, our Canadian ambassador in Trumpland, couldn't hide his irritation.

Following a trade commission hearing on the American bid to put astronomical tariffs on the sale of Canadian-made Bombardier jetliners, he met with reporters. "The whole thing" he alleged, "is quite absurd."

Illogical for starters, he noted, is rival Boeing's principal grievance, it being that Ottawa heavily subsidizes Bombardier. As if, Mr. MacNaughton pointed out, Washington doesn't subsidize Boeing – to the tune of billions. Hypocrisy anyone?

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But the low-key envoy wasn't only in high dudgeon about aircraft. On a broader canvas is the collateral damage brought on by the protectionist mentality at the White House. The anti-trade rhetoric "has given U.S. companies the permission to take action they wouldn't have taken before," he said, Boeing being just one case in point.

In dealing with the Trump administration, it's been a year of frustration for Prime Minister Justin Trudeau and his cast. Try as they might – and they've put up a rational fight – they haven't been heard. The foremost example has been the Republican administration's threat to abandon the continental free-trade pact. It's still in play, in a Sword of Damocles sort of way.

U.S. presidents, it need be said, don't owe Canada anything. They have their own interests to tend to, as Donald Trump has amply demonstrated.

Where Ottawa's exasperation lies is in trying to locate where, on any given day of the week, Mr. Trump's head is situated. The North American free-trade agreement zigzags offer an example.

In his election campaign, Mr. Trump said NAFTA was the worst deal ever. Sorry folks, it's gone. But once elected, he had an abrupt change of mind. In March, he said that in the case of Canada it only needed tweaking.

In April, he had an abrupt change of mind. He let it be known that he was about to issue a termination notice of the treaty. But he held off. Then in the summer came a change of mind. Phone transcripts of a call to the Mexican leader revealed Mr. Trump saying he had no problems with Canada on NAFTA.

But in the fall came a change of mind. His negotiating team put forward five bombshell demands on NAFTA changes that are virtually impossible for Ottawa to meet.

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Frustration anyone? How is the Prime Minister supposed to deal with a President whose modus operandi is the hairpin turn?

The NAFTA threat has been one of several difficult consequences for Canada of Mr. Trump's startling election triumph.

Another has been Ottawa's big hike in defence spending. With Mr. Trump, the Trudeau government decided, perhaps precipitously, that Canada could no longer rely on American protective power and the type of collective security presidents formerly embraced. Up went arms spending.

Another consequence was Mr. Trump's killing of the Trans-Pacific Partnership trade deal. It was a gift to China. It left the Ottawa Liberals scrambling for new deals and occasioned the recent unsuccessful Trudeau mission to the Middle Kingdom to curry commercial favour.

Another has been the American withdrawal from the Paris climate accord which Ottawa strongly supported. It has a stake in Washington's work on the environment. Under Scott Pruitt, the U.S. Environmental Protection Agency is being turned into its opposite.

An unwelcome development also is the Republicans' sweeping tax-cut package. Canada held an advantage over the United States in luring investment by virtue of its very low 20-per-cent corporate tax rate. The American rate was in the 30s. The Trump package slices it to 21 per cent.

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It's not all bad. The Keystone XL pipeline favoured by Mr. Trudeau was given the go ahead. On the foreign front, while there's been a lot of bellicose White House rhetoric, it's been a year of relative peace. On the issue of branding, the heavily scorned, morally challenged, inwardly looking Trump regime has served to enhance the image of Canada as a forward-thinking, fair-minded, open society.

A big plus for Canada is the high-flying economy over which Mr. Trump presides, making American markets for the northern neighbour more bounteous.

But that prompts yet more frustration in our country's capital. The Canadian and American economies are finally coming out of a long stretch of low-growth doldrums. Things are looking up. Why jeopardize this, as the Canadian ambassador puts it, by moving to a new era of protectionism?