David A. Andelman, Executive Director of The RedLines Project, is a contributor to CNN, where his columns won the Deadline Club Award for Best Opinion Writing. Author of "A Shattered Peace: Versailles 1919 and the Price We Pay Today," and translator of "An Impossible Dream: Reagan, Gorbachev and a World Without the Bomb," he was formerly a foreign correspondent for The New York Times and CBS News. Follow him on Twitter @DavidAndelman . The views expressed in this commentary are his own. View more opinion on CNN.

(CNN) From North Korea and China, across Russia and Europe, world leaders this holiday season have been raising both direct and oblique challenges to the United States. Above all, these messages should give Trump pause before he continues what is promising to become a headlong slide into an abyss of isolation.

Most of the leaders, especially those heading democracies around the world, understand how far Trump has drifted from the traditional American values that have so long been prized abroad. If Trump listens carefully to these New Years' messages from democrats as well as autocrats, and is able to make informed decisions that may help form stronger alliances -- while seizing opportunities to stand strong against threats to American interests -- he may perhaps find a path out of the wilderness into which he has plunged his presidency and the American people.

North Korea

Six months after Kim Jong Un met with President Donald Trump in Singapore and signed a vague pledge agreeing to work toward complete denuclearization in exchange for lifted sanctions, the two countries remain deadlocked on how to achieve this. On Tuesday, Kim issued a televised address from Pyongyang -- where the new year arrived 14 hours ahead of Washington -- and wasted no time throwing down the gauntlet.

"If the US does not keep the promises it made in front of the world, misjudges the patience of our people, forces a unilateral demand on us, and firmly continues with sanctions and pressures on our republic, we may be compelled to explore new ways to protect our autonomy and interests, and establish peace and stability on the Korean peninsula," Kim said

Clad in a dark western suit, Kim sat on a leather sofa in front of a fireplace with portraits of his father and grandfather behind him and said he'd be delighted to meet with Trump a second time. But Kim would leverage a meeting to demand -- either as a precursor for negotiations or a necessary condition for disarmament -- the end of US sanctions and the withdrawal of American forces from South Korea.

It will be worth watching to see how Trump's new Acting Secretary of Defense Patrick Shanahan might react to the prospect of American withdrawal, if the President were foolish enough to even consider such a proposal without solid proof of progress toward an end to the North Korean nuclear program.

China

In his New Year's message , Chinese President Xi Jinping avoided any direct mention of the tariff war with the United States, and pledged to push ahead with his Belt and Road development, which will stretch from Asia to Europe and into Africa, and promote trade.

In addition to the ambitious multi-billion dollar initiative -- which is seen as a major challenge to American interests as China wrestles for global dominance -- Xi said, "Looking at the world at large, we're facing a period of major change never seen in a century. No matter what these changes bring, China will remain resolute and confident in its defense of its national sovereignty and security." In short, Xi is pushing a "China first" agenda, and posing quite a challenge to Trump's "America first" strategy.

Xi did also send a separate message to Trump that appeared somewhat more conciliatory. The United States and China are counting down the days until the end of the 90-day trade war truce that was agreed upon last month, and Apple is already warning investors about slowing iPhone sales in China, which CEO Tim Cook blamed in part on "rising trade tensions."

Xi pointed out that "history has proved that cooperation is the best choice for both sides," and Trump responded that it was his priority to promote constructive US-Chinese relations, according to the official Chinese news agency Xinhua. The two leaders also spoke by telephone, and Trump characterized their conversation as a "long and very good call," before adding that the trade talks were progressing well.

If Trump and Xi can't find a way to resolve their trade war in 2019, there will be consequences far beyond the dangerous economic landmines of such an impasse. And while Xi's message was addressed to his own people, it's clear that Trump will face challenges from Beijing as China will continue trying to muscle its way toward global dominance -- as well as regional dominance in the South China Sea, which carries about a third of global shipping.

France and Germany

Both the leaders of France and Germany faced serious questions regarding their leadership this past year, and both President Emmanuel Macron and Chancellor Angela Merkel used their annual messages to reassert themselves yet again in sharp contrast to Trump.

Macron delivered a law-and-order message to his people, amid ongoing "yellow vest" demonstrations against his economic and social policies. The French leader, who has appealed frequently for an end to nationalism, said , "We are free in our country only because generations before us fought not to suffer from despotism or any tyranny, and this freedom requires a republican order. It requires the respect of each and all opinions."

This isn't the first time Macron and Trump have expressed differing views. The US President previously blasted Macron for his push for a European defense force . Just last week, Macron spoke out about the need for France and Europe to remain in Syria and battle ISIS.

In what appears to be a veiled rebuke of Trump's foreign policy strategy, German Chancellor Angela Merkel said, "We will only master the challenges of our times if we stick together and collaborate with others across borders." Though effectively a lame-duck leader, having lost her leadership of the ruling Christian Democratic Union with plans to step down when her current term as chancellor ends in 2021, Merkel told her people , "We are committed to a more robust, more decisive European Union," adding that nationalism remains the leading threat to the international order.

Merkel also appeared to take swipes at Trump as she suggested that climate change, managing migration and combating terrorism required international cooperation. "We want to resolve all these questions in our own interest, and we can do that best if we consider the interests of others," she said . "That is the lesson from the two world wars of the last century. But this conviction is no longer shared today by everyone, and certainties of international cooperation are coming under pressure."

European leaders seem increasingly prepared to break from Trump and all he represents. Trump will have a hard time in the new year amid increased support for a European defense force, as well as a determination to retain a foothold in the Middle East. Trump is also likely to face challenges on climate change and sanctions on Iran

Russia

President Vladimir Putin set up a series of difficult challenges to the international order in a host of bilateral messages to world leaders including Trump, Syria's Bashar al-Assad, and Turkey's Recep Tayyip Erdogan. "Through their joined efforts, Moscow and Ankara are making a decisive contribution to fighting terrorism in Syria and advancing the process of political settlement in that country," according to a press release from the Kremlin , describing Putin's letter to Erdogan.

At the same time, he promised Bashar he would "continue to provide all-round assistance to the government and people of Syria in their fight against terrorism and efforts to protect state sovereignty and territorial integrity," the press release states

This suggests that in the new year, Putin intends to cement his dominance throughout the region as Trump prepares America's withdrawal.

Separately, to Trump, Putin proposed a summit conference in the new year with an extensive agenda.

In his broader message to his own people, Putin urged that they work together to improve the quality of life in Russia. He said , "We never had any help in these endeavors, and never will," an apparent suggestion that they should look to no early end to sanctions that continue to cripple the Russian economy.

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All these New Year's messages make it clear that this is not the time for impulsive or ill-considered decisions. How Trump responds to these challenges -- and how deeply he understands and navigates the powerful forces at work across Asia, the Middle East, and Europe -- will determine the fate of the United States over the next year.