David A. Andelman, visiting scholar at the Center on National Security at Fordham Law School and director of its Red Lines Project, is a contributor to CNN and a columnist for USA Today. Author of "A Shattered Peace: Versailles 1919 and the Price We Pay Today," he was formerly a foreign correspondent for The New York Times in Asia and Europe and the Paris correspondent for CBS News. Follow him on Twitter @DavidAndelman . The views expressed in this commentary are his own.

(CNN) Donald Trump may have just torched his last real friend in the Western alliance, someone he could have counted on when the going gets tough. In what was supposed to be a frank exchange of views, French President Emmanuel Macron apparently got the full Trump treatment the other day when he tried in a phone call to level with the one world leader who does not support being leveled with, even coming from his closest confidants.

And with a succession of battles looming on the trade front, on Iran's nuclear future, on migration and climate change, not to mention a dicey North Korean summit in Singapore, Trump needs all the friends he can get. Now, Trump seems to be flying entirely solo, as Macron, long an apparently reliable wingman, peels off, reaching a long-awaited, though not unexpected, reconciliation with his principal challenger for European leadership -- German chancellor Angela Merkel.

Defaulting to confrontation and pique seems to be how two sources familiar with the recent telephone call between Trump and Macron described it to CNN. How is this even possible? What other president could possibly have reacted in this manner to frank criticism from an ally and called it a "win?"

The saddest part of all is that Trump apparently failed to even comprehend the context. Macron and Merkel, who herself has had a pretty frosty relationship with Trump, have been getting decidedly chummy themselves recently.

On Sunday, Merkel gave a long-desired endorsement to one of Macron's pet projects -- a joint European military "intervention force" that could take action around the world, and without relying on what European leaders have come to view as an increasingly unreliable ally in the form of Trump's America.

But there are other issues that should be even more troubling for Trump in Merkel's statement and Macron's phone call. Merkel now sees such a joint military force as a way of keeping Britain involved in Europe's defense and the United States very much on the periphery.

At the same time, a European Union summit at the end of June, following this week's G-7 summit in Canada and Trump's meeting with North Korean dictator Kim Jong Un next week in Singapore, promises a whole new set of challenges that Washington is barely prepared to take on, and indeed seems only to be intensifying by the day.

Merkel's interview on Sunday with her nation's leading daily, the Frankfurter Allgemeine, hit every major hot button for trans-Atlantic as well as pan-European relations -- migration, finance, as well as defense and security.

While still tiptoeing around Macron's desire for a far more integrated European finance system, she did back the idea of a European monetary fund that could help out some of Europe's unstable poor sisters. She also called for common asylum policies for immigrants from Africa, the Middle East and beyond, as well as European border police forces and a pan-European migration agency to assess asylum requests.

Of course, little of this rhetoric appears at all congruent with what President Trump has been proposing for the United States -- far more restrictive immigration policies, few grants of asylum and virtually no coordination with foreign allies or partners on such issues, not to mention a border wall that remains in a state of suspended animation.

Already well-known and carefully enunciated by both Merkel and Macron, as well as Britain's Prime Minister, Theresa May, have been the feelings on the most bristling issue between Europe and Trump: trade and tariffs. Europe, Merkel has said, is "resolved to defend its interests within the multilateral trade framework," adding that she had the agreement of both May and Macron.

And then came the phone call between Trump and Macron -- focusing, as a subdued White House statement observed, on trade and immigration, as "both leaders discussed the migration problem in Libya, and timelines to solve it. President Trump underscored the need to rebalance trade with Europe." As it happens, the call took place the same day the administration announced its decision to levy stiff tariffs on European steel and aluminum exported to the United States; Macron said the decision was "not only illegal, it is a mistake on many points." Now there is the overhanging threat of European retaliation, none of which seems to have been in the least eased by the Macron-Trump phone call.

But hang in there, the Europeans aren't finished. Later this week is a chat on the phone with Theresa May in London, where Trump is still planning a long-anticipated and in many British circles feared, "working visit" next month where he's expected to meet the Queen

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First, though, he has to get through the G-7 and this is where the rubber is truly expected to hit the road. Canada's Prime Minister Justin Trudeau, the meeting's host, is clearly livid over Trump's decision to order national-security-inspired tariffs on Canadian steel and aluminum, that he described on NBC's Meet the Press on Sunday as " insulting ."

Moreover, the Paris climate agreement, from which Trump withdrew the United States early in his presidency, will also be on the table, not to mention a central question as to whether the final communique will suggest, as it did last year, that the G-7 is really the G-6 plus Donald Trump's America -- yet another testimony to "America First" being very much America alone.

Still, President Trump should practice diligently in front of a mirror his best smile -- the kind he was so eager to trot out for his Oval Office session with North Korean emissary Kim Yong Chol, bearing the cartoonishly-large envelope with a letter from Kim Jong Un -- and suggest that he is at least prepared to listen to reasonable voices even if he thinks he really knows best. For America does very much need friends in Europe, as well as north and south of our own borders.