Trade. North Korea. Iran. The dangers awaiting Trump.

Barack Obama met with Donald Trump at the Oval Office on Thursday following his spectacular election upset on November 8. While the president-elect promptly promised to "put America's interests first, but deal fairly with everyone", many U.S. allies are nervous about what his win will mean for U.S. policy. That means he now has to begin a major campaign of re-assurance, and prepare for a host of challenges in a world full of potential danger.

Trump is starting to receive enhanced intelligence briefings and his in-tray is vast. In the Middle East, key offensives are underway against Islamic State in Mosul, Iraq, and Raqqa, Syria. In Asia, political tensions are growing in South Korea, where President Park Geun-hye faces pressure to resign at the same time the nuclear stand-off with North Korea has intensified. In Europe, the migration crisis is adding to concern in the continent over the future of the European Union post-Brexit.

One key area of uncertainty for allies is over Trump's trade policy. He spoke out against agreements like the North American Free Trade Agreement (NAFTA) and the controversial Trans-Pacific Partnership (TPP) during his campaign; it remains to be seen what specific posture he will take toward these deals. In particular, the president-elect must decide how hard to push back if Obama decides, before his presidency ends in January, to have a final push at getting congressional passage of the controversial TPP. TPP, which may now be dead-on-arrival in Congress, is a massive trade deal with 11 other countries in the Americas and Asia-Pacific (including Australia, Canada, Japan, New Zealand, Malaysia, and Mexico) that account for about 40 percent of world GDP.

This will be a big early call for Trump given that many Republicans want the deal to entrench U.S. influence in Asia-Pacific in the face of a rising China. If TPP collapses, it will intensify doubts about U.S. leadership in the region, potentially undermining Trump's leverage with some local allies on other key issues.

The conundrums now confronting Trump aren't limited to these issues. Indeed, there are some indicators that geopolitical risks are now at their highest level since the end of the Cold War.

Other foreign policy fault lines include tensions with China over the latter's territorial claims in the South China Sea; continuing instability in Afghanistan and Libya, and the bleak prospects facing the Israeli-Palestinian peace process. Meanwhile, continuing hostilities in Ukraine means that Washington's relations with Moscow are perhaps most strained than at any point since Soviet Communism's collapse.

The bilateral relationship with Moscow under Trump will be a special source of scrutiny for many internationally. His relationship with Putin has been warm, rhetorically, and Trump has been criticized for calling NATO "obsolete".

This world of dangers now facing Trump underlines how much the optimistic hopes of how the post-Cold War world might look have been dashed. The vision of a universal order of liberal, capitalist, democratic states living in peace and contentment has been replaced by a reality in which authoritarian states such as Russia appear to many to be a growing force on the world stage; international terrorism remains a concern a decade and a half after 9/11, and unstable places like North Korea have acquired nuclear weapons.

Trump is among those critics of Obama and Democratic presidential nominee Hillary Clinton who see these concerns as a result of weak leadership in Washington over almost eight years. This is an oversimplification.

To be sure, the United States remains the most powerful country in the world — certainly in a military sense. It can still project and deploy overwhelming force. However, despite some of his rhetoric during the campaign, Trump hopefully recognizes Washington is not, to use a piece of jargon from international relations, an all-powerful hegemonic power.

Trump and other unalloyed critics of Hillary Clinton and Obama also often fail to acknowledge that, while 2016 may be a year of high political risk, the current international landscape also contains opportunities for greater stability through careful international leadership.

One example is last year's nuclear deal with Iran and six world powers — the United States, China, Russia, United Kingdom, France, and Germany. The agreement, which Trump criticized during the campaign, theoretically opens up the possibility of warmer ties between Tehran and the West, and could also enhance global nuclear security.

However, neither Trump nor many Republicans controlling Congress are committed to the deal. While Trump has said he would re-negotiate it, he has also said that he opposes all aspects of it — and has called Iran the "biggest sponsor of international terrorism" to boot.

Meanwhile, the rise of China, which has now surpassed the United States as the world's largest economy on purchasing parity terms, represents one of the biggest transformations in global affairs in recent years. This development has potential to be either a growing source of tension with Washington under the new Trump presidency, or develop into a fruitful partnership.

Growing bilateral cooperation is possible if, under Trump, the two countries can increasingly find ways to resolve harder power disagreements, including South China Sea territorial claims, while cooperating on soft issues like climate change. By contrast, bilateral rivalry is possible if Beijing's military strength continues to grow rapidly and the country embraces a more assertive foreign policy toward its neighbors in Asia.

Going forward, the success of Washington in helping manage the complexity of global affairs will increasingly depend upon cooperation of others, both competitors and allies. So much will now depend on whether Trump can truly deliver on his post-election pledge to "have great relationships" and seek "partnership" with other key world powers.