The NAFTA negotiations this week in Montreal will give us a good sense of whether a new agreement is possible. Canada and Mexico are coming to the table with ideas on the “poison pills” but is the United States ready to negotiate?

The test will come on three issues:

– Can we preserve dispute settlement as a check against unfair protectionism?

– Can we find an equitable formula around trilateral content rules for cars, our most traded commodity?

– Will government procurement stay open to all three nations?

If we cannot resolve these issues, then we have to look to Plan B, life without the North American free-trade agreement.

Foreign Minister Chrystia Freeland’s “hope for the best, prepare for the worst” is a fair characterization of NAFTA’s prospects. The Trump administration continues to ramp up protectionist actions against foreign competition. In recent months, the United States has hit Canada with punitive tariffs on lumber, jets and now newsprint.

U.S. President Donald Trump’s repeated threats to rescind NAFTA is galvanizing hitherto-silent U.S. support into action. The farm community and business, two vital groups in the Trump coalition, want NAFTA improved, not rescinded. Surveys show a majority of Americans like NAFTA. Senators and members of the House of Representatives, especially those in the Midwest and from Texas, are now pressing the President to do no harm to NAFTA.

Canada and Mexico have launched unprecedented outreach campaigns. Canadian envoys have met with more than 65 governors and lieutenant-governors and more than 265 congressmen. We are finding allies. We will need them if Mr. Trump rescinds the agreement or if any new deal reaches Congress.

Canada and Mexico must stay engaged in what should become a permanent campaign to cultivate the biggest market in the world.

But the future of NAFTA now depends on the outcome of the American internal debate.

Canadians faced their moment of truth on trade in 1988. We fought an election over closer economic relations with the United States. It brought prosperity, not, as the critics warned, a loss of sovereignty. Mexicans faced a similar moment in 1994 when they embraced the NAFTA.

For both Canada and Mexico, freer trade proved that we could compete, not just with the U.S., but internationally.

Freer trade also became a catalyst for domestic economic reform.

For Canada, the restructuring included the introduction of a national value-added tax, the GST. Federal and provincial governments cut their deficits. For Mexico, NAFTA restructuring supported democratic change in 2000 after 71 years of one-party rule. More recently, it helped spur the “Pacto por Mexico” reforms to education, finance, labour and energy.

For Americans, NAFTA is a litmus test of its place in the world. Will they replace the rules-based order, created and sustained by the United States for 70 years, with Mr. Trump’s vision of America First? Will Americans set aside their traditional generosity towards other countries with one based on mercantilism and beggar-thy-neighbour?

For the first time, the most important global economy wants to renegotiate a trade agreement by increasing trade barriers so as to balance its trade. It’s a world of big rolling over small. Middle powers like Canada and Mexico need to push back.

Previous U.S. administrations, both Republican and Democrat, saw U.S. internationalism not as an act of charity, but as reflecting U.S. values and principles. As practised by Roosevelt through Reagan and Obama, the United States used its weight to better the global condition, willing to give more than it received. This is the “indispensable nation” that Ms. Freeland described when she laid out the Trudeau foreign policy last June. She described a United States that sustains the global order, for the greater global good, through a network of alliances, trade agreements and international institutions.

Mr. Trump’s “America First” breaks with this American tradition. Will Congress and the courts go along with Trumpism? While Canada and Mexico prepare for the worst, we must stay engaged with the many Americans who see the world, and America’s place in it, differently than Mr. Trump. Ultimately, Trumpism is a test of how Americans see themselves and their place in the world.