Angry American voters who feel slighted by the Washington establishment have had their say. A stunned world must now come to terms with what the election of Donald Trump as the 45th President of the United States means for global stability in the years ahead. The world has some time to consider the full implications of Trump’s victory, because he will not take office until January 20, 2017, and he will then spend several months staffing his administration with the men and women who will actually formulate and implement its policies.One thing we already know is that authoritarian rulers around the world can rest easier. They will not hear any more harsh words from the US about their regimes’ contempt for democracy, freedom, or human rights. The American goal of making the world safe for democracy will now be replaced by a policy of “America first,” a sea-change in US foreign policy that is already likely arousing jubilation in Russian and Chinese halls of power. We also know that Trump’s victory jeopardizes world trade. Trump has promised to ditch the 12-country Trans-Pacific Partnership, impose punitive tariffs on Chinese imports, and unilaterally renegotiate the North American Free Trade Agreement. This is the last thing the world needs right now, given that trade – and the global economy itself – is already struggling.Trump has promised to strengthen the US military and national-security regime, and to aggressively pursue the Islamic State and jihadist threats around the world. But eliminating the Islamic State and bringing genuine stability to the Levant will require far more than what he has proposed so far. And while he will probably revise his overly casual comments about nuclear weapons, we cannot ignore the possibility that the world will enter a new period of arms proliferation and instability. Trump has said that he will renegotiate the Iran nuclear deal, and he has vowed to renege on the US’ carbon-reduction commitments under the Paris climate agreement. These are two of the international community’s only significant diplomatic achievements in recent years. The consequences of a US retreat from them are anyone’s guess. In any case, global stability will certainly suffer.Trump’s foreign-policy strategy is based on remaining unpredictable. But while some caginess in international relations has frequently been part of US policy (just ask Henry Kissinger), predictability is at the core of America’s system of alliances, relationships, and friendships, which it has cultivated over many decades. Damaging America’s standing as a good-faith actor on the world stage would set the scene for widespread instability.When Trump takes office, he will have to move quickly to reassure America’s friends and allies around the world. Otherwise, they could seek alternative relationships with the US’s adversaries or other unsavory players.The European Union will play a central role in the drama ahead, because it has long been America’s primary partner on global issues, and vice versa. Trump, however, has praised the United Kingdom’s decision to leave the EU, and his only European friends so far are figures such as UK Independence Party leader Nigel Farage, who led the UK’s Brexit campaign and even stumped for Trump in the US. Whether he intends to or not, Trump will give populists and nationalists such as Farage a boost in the coming months and years.Trump may find out too late that a fractured Europe is a less stable Europe, and that there are US adversaries poised to exploit the opportunity of European disunity. Russia, for its part, is explicitly trying to undermine the EU, and to change the rules of the game in Europe. Russian President Vladimir Putin may now view Trump as a new partner in his revisionist project; but he could very well overplay his hand, too.The world will have to give Trump time to pivot from his anger-driven campaign to responsible governance, which is the only way that the US can maintain its global influence. He will have to make his choices for Secretary of State, Secretary of Defense, and National Security Adviser early, and the world will scrutinize his appointees carefully.Trump may turn out to make good choices. But, given the tenor of his campaign, confidence in the US on the part of its foreign partners is at low ebb. With Trump’s victory, the world has decisively entered a period of increasing unpredictability and instability. Global challenges are multiplying, and the international order as it has existed since the end of World War II is under grave threat. Even under the best of circumstances, Trump’s election has undoubtedly reinforced these disturbing trends.