David A. Andelman, a frequent contributor to CNN Opinion and columnist for USA Today, is the author of " A Shattered Peace: Versailles 1919 and the Price We Pay Today ." He formerly served as a foreign correspondent for The New York Times and Paris correspondent for CBS News. Follow him on Twitter @DavidAndelman . The views expressed in this commentary are his own.

PARIS President Donald Trump, back in Washington from the G20 summit and relaxing Sunday at his Virginia golf club, has managed to leave behind a succession of landmines likely to explode in the coming weeks and months. With each explosion, the United States is increasingly likely to find itself as a pariah nation on the global stage.

Some of these explosive issues had been long anticipated -- following weeks, even months, of vitriolic Trump tweets that effectively poisoned the atmosphere for many world leaders and especially for their top aides who were responsible for crafting the agenda and will be in charge of shepherding these issues going forward.

Let's take a closer look:

Climate change

The United States is as isolated as it has ever been on climate change, which is hardly surprising as Trump was the only leader to withdraw his nation from the Paris COP21 climate agreement, signed by 175 countries . The G20 final communique in Hamburg was the first formal indication that no one is prepared to follow Trump out the door.

Moreover, French President Emmanuel Macron used the G20 platform to call for a global climate summit on December 12, the second anniversary of its drafting, with the aim of moving the pact forward through public and private financing of projects worldwide.

Trade

With President Trump telling British Prime Minister Theresa May, as one senior government source told The Sunday Times of London , "that the United Kingdom will thrive outside the EU," the pressure only intensifies for May to make good both on a hard Brexit and a rapid negotiation of a favorable trade pact with the United States.

At the same time, just as the G20 was about to get underway, the EU announced it had already negotiated its own trade deal with Japan, following the framework for a similar pact with Canada. Indeed, with Trump standing silently by, Japanese Prime Minister Shinzo Abe called his new EU arrangement a "model for the 21st century."

Ironically, the United States has failed even to begin any meaningful bilateral negotiations for such free trade mechanisms with either the UK or Japan, though bilateral pacts are what Trump has advocated loudly and repeatedly. Now, benchmarks have been set for any such negotiations going forward -- yet another potential landmine for Trump's business agenda.

Next up? German Chancellor Angela Merkel suggested an EU-China investment treaty may not be far behind. Indeed, the day before the G20 got underway, with Merkel and Xi looking on, China signed a $22 billion deal to buy 140 planes from the European Airbus consortium. New aerospace jobs may now go to European workers.

Russia

Barely 24 hours after Trump and Putin glowed over a ceasefire in southwestern Syria, the fifth such agreement in the past six years went into effect. Still, both Russia and the United States are working out how to monitor and enforce it. Moreover, there's no hint here that Russia is any closer to lifting its support from the Bashar al-Assad regime, or that the United States is any closer to finding a path forward for its own interests.

And then there's the cybersecurity pact that Trump and Putin announced -- the creation of a somewhat vaguely defined joint unit to guard against the use of cyber tools in election hacking, and which Florida Republican Senator Marco Rubio promptly denounced as "partnering with Syrian President Bashar Assad on a Chemical Weapons Unit." How long will that take to blow up, and how likely is it simply to give the Kremlin cover on cyber shenanigans in much of the world?

China and North Korea

Let's start with the White House press release calling Chinese President Xi Jinping the President of the Republic of China, which is the official name for Taiwan, just minutes after Trump was waxing eloquent about their "wonderful relationship." Both leaders tried to plaster smiles on their faces, but there is no getting around Xi's visit to Moscow en route to the G20, when leaders of both nations shook hands on an agreement that would ban North Korean missile tests as well as US-South Korean military drills.

The United States has suggested that this is a highly asymmetric agreement -- one that North Korea is likely to breach without warning and that leaves South Korea and Japan deeply vulnerable. It also takes no steps toward even more vital efforts to restrain North Korea's efforts to develop a deliverable nuclear weapon.

Mexico

All but lost in the excitement of meetings Trump held was his first face-to-face meeting with Mexican President Enrique Pena Nieto since Trump took office. With the Mexican leader sitting by his side, Trump reiterated publicly , yet again, that Mexico will "absolutely" pay for the wall on its northern border. Pena Nieto failed to challenge this embarrassing boast, which promptly inflamed opinion back home over the "cowardice" of the Mexican leader in dealing with an American President who apparently has little appreciation or sensitivity for Mexican feelings. Clearly, the path forward for relations between these two neighbors has only been re-paved with ill intentions.

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Effectively, Trump left the G20 in precisely the place he wanted, but as seen through a fun house mirror. By turning his weekend's focus to a succession of bilateral schmooze fests, he left the leadership of the rest of the world to the likes of Merkel, Xi , Macron, even Putin.

His "America First" philosophy has left a vacuum going forward that will only be filled by others with their own interests and motivations. In an increasingly globalized world, an American President is willingly contributing to a chasm increasingly impossible to bridge.