More than a century ago, President Theodore Roosevelt created a "Roosevelt Corollary to the Monroe Doctrine", which expanded on 19th century claims of US pre-eminence in the Western Hemisphere to keep Europeans out.
During the Cold War, a series of US presidents butted heads with European leaders over how best to manage relations with the Kremlin. The most recent Republican President, George W. Bush, adopted a unilateral approach to the US "War on Terror" to avoid European limitations on US action.
But Trump is the first President to behave as if Washington would be better off if the European Union broke apart. We saw this when Trump reportedly suggested to French President Emmanuel Macron in June that France exit the union, while offering a bilateral trade deal as a kind of incentive.
We saw it when Trump warned British Prime Minister Theresa May that a "soft Brexit", one that preserves strong UK-EU commercial ties, would kill the chance for a new UK trade deal with the US.
We see it in Trump's efforts to build a relationship with an Italian Government that represents the largest threat to the future of the Eurozone, whatever that Government says about its immediate intentions.
"The European Union, of course, was set up to take advantage of the United States," Trump told a crowd of cheering supporters in June. We see it in Trump's drive to bring Russia back into the G7 and to undermine the coherence of the Atlantic alliance. "Nato is as bad as Nafta," he reportedly told his G7 counterparts.
At last month's Nato summit, Trump explicitly questioned why the US should honour the alliance's treaty commitment to collective security. Why defend Montenegro, a country that has been "extremely aggressive", he asked. Vladimir Putin couldn't have said it better.
Trump admires leaders like Putin, Xi Jinping, and Saudi Crown Prince Mohammad bin Salman in part because he envies the lack of domestic checks on their authority. It's easier to talk tough when no one is allowed to talk back.
He also prefers to negotiate with men he believes have the power to make deals, leaders unburdened by the competing demands of sponsors and constituents.
The US President also prefers relationships that are one-on-one and highly personalised over multilateral alliances that require compromise and respect for the interests and views of others. Alliances limit options and drain resources.
They are governed by common values as well as common interests. Perhaps Trump believes that, in a world ruled by national leaders unencumbered by checks and balances, American power would make him the world's most powerful man.
On the domestic front, limits on Trump's power will continue to frustrate him. He will struggle to find anyone who can rid him of the meddlesome Robert Mueller. Courts will assert their authority. Reporters will continue to report.
America's central bankers will shrug off Trump's pressure for his preferred policy. The opposition party will oppose him wherever possible, and voters may decide in November to strip his party of its majorities in Congress.
Yet, Trump's threat to the international system, which is based on interlocking alliances and consensus-based organisations governed by rules and laws, is much more potent.
At a time when increasingly prosperous and influential China offers the world a credible alternative to democracy and rule of law, and as populist pressures and technological changes make authoritarian control easier to build and maintain, Trump's attacks on allies and alliances already have real consequences.
• Ian Bremmer is the president of Eurasia Group and author of Us vs Them: The Failure of Globalism
