They were laughing at him, and it made President Trump angry.

So when asked about the video clip that appeared to show NATO leaders commiserating about Trumpian behavior, the president was snappish. “Well, he’s two-faced,” Trump barked about Canadian Prime Minister Justin Trudeau (who was joking to counterparts about Trump’s self-promotion).

But Trudeau wasn’t alone in issuing Trump a put-down in London. The open disdain shown by some allies at NATO’s 70th-anniversary celebration this week reflects how Trump is regarded worldwide, both by longtime friends and foes.

I have watched the shift in attitudes in my travels since Trump was elected, including to Russia, the Mideast, Europe, and a just-completed trip to China. The president is seen as erratic, untrustworthy, and interested in little beyond self-promotion or making a profit. And oh yes, as easily manipulated by flattery, especially by the autocrats he admires unreservedly.

And so ill-informed that he could unintentionally drag America into a war.

The dangers these behaviors present were well laid out by French President Emmanuel Macron in an interview with the Economist just prior to the NATO meeting. The French leader said the absence of American leadership was leading to “the brain death of NATO.” He added that America under Trump was showing signs of “turning its back on us,” meaning abandoning its commitment to the alliance, which drastically undercuts the viability of the organization.

Case in point, Macron said in the interview, was Trump’s pulling U.S. troops out of northeastern Syria, and abandoning our Kurdish allies, with no prior notice to them or to European countries such as France, which also had troops in that theater. “You have no coordination whatsoever of strategic decision-making between the United States and its NATO allies,” Macron said. “None.”

» READ MORE: Talk of a new Cold War between U.S. and China is misleading | Trudy Rubin

At the London meeting, as he met the press alongside NATO Secretary General Jens Stoltenberg, Trump called Macron’s remarks “very insulting.”

Yet over 40 minutes, while questioned repeatedly about his NATO strategy, Trump showed himself clumsily unable to utter one sentence on the topic. No matter what he was asked, he returned over and over to his single talking point: that, thanks to him, NATO members upped their defense spending (although, even on the numbers, he kept making inaccurate claims).

As Macron pointed out, in a testy public exchange with Trump, NATO has other challenges besides “just numbers.”

Yet, in public remarks, Trump seemed not to have a clue or a care as to what NATO should actually do in the future. It was left to Stoltenberg to talk about the need to continue the fight against terrorism and the implications of a rising China. (It is little wonder that NATO members fear Trump might withdraw from the alliance if he wins in 2020.)

Trump reportedly returned to his list of grievances about inadequate defense spending in a closed-door session, rather than focus on strategic issues. To emphasize his single-minded point, the president ate lunch with the leaders of the eight NATO members who are meeting alliance spending guidelines.

It was left to an angry Macron to point out the strategic cost of the president’s recent kowtow to Turkish President Recep Tayyip Erdogan, an autocrat whom the president admires. Trump abandoned the Syrian Kurdish allies, who defeated ISIS, to the tender mercies of Turkey, which has helped ISIS for years. “When I look at Turkey, they are fighting against those who fight with us,” said Macron. “Who is the enemy today?”

And over the NATO meeting hung the shadow of impeachment hearings, in which the White House has promoted a wholly debunked conspiracy theory that Ukraine, not Russia, was responsible for hacking the 2016 elections. NATO allies, some of whose elections were or are currently being hacked by Russia, know that this is a total lie. So does the world.

One of the more bizarre lies Trump told in London was his flat denial that he knew Britain’s Prince Andrew (who has been linked to the Jeffrey Epstein sex scandal). The president was photographed multiple times with the prince, who partly hosted him during a state visit to the United Kingdom in June. And when it came to Britain, Trump was clearly miffed that Prime Minister Boris Johnson was anxious to avoid photos or contact with the U.S. leader, since that could cost him votes.

The sense of a leaderless NATO was palpable, despite efforts by Stoltenberg to paper it over.

Trump’s NATO appearance solidified the image of a U.S. president bereft of any long-term strategy toward Europe, Russia, or China, who (falsely) believes the world agrees with his self-assessment that he is a “stable genius.” Instead, world leaders see Trump as abdicating America’s historic role while Russia, China, and other adversaries fill the vacuum.

So rather than funny ha-ha, the NATO laughter at Trump’s expense should serve as a warning: America’s withdrawal from global leadership under this president is already endangering U.S. security. It will cost the country dearly should he be reelected to another four-year term.