How a second Trump presidency could reshape the world

The results aren't in yet, but if Donald Trump ends up winning the 2024 presidential election and regaining the presidency, he could radically reshape international politics.

Trump has made very clear on the campaign trail that he believes major changes to US foreign policy are necessary: "We have been treated so badly, mostly by allies ... our allies treat us actually worse than our so-called enemies," Trump told the audience at a September campaign event in Wisconsin . "In the military, we protect them and then they screw us on trade. We're not going to let it happen anymore."

Those aren't empty promises. Presidents have wide latitude on foreign policy and can enter or nix many international agreements unilaterally.

"It really does vary, agreement to agreement, in terms of what the exit criteria are, but there are very few where a congressional approval for withdrawal is required," Jennifer Kavanagh, senior fellow and director of military analysis at Defense Priorities, told Vox.

In his first term, Trump pursued what he called an "America First" foreign policy, which saw him withdraw from major international agreements , launch a trade war with China , verbally antagonize allies , and attempt complex negotiations with several of the US's adversaries .

This campaign season, he has promised to continue attempts to dramatically alter or otherwise hamper international agreements, including the NATO security alliance , in ways that could fundamentally weaken the US's place in the global order.

Of Trump's stated foreign policy positions, his planned protectionist trade policy would likely be the most immediately damaging to Americans; his proposed tariff increases would spark a global trade war and drive up prices for American consumers. In the longer term, his ideas about the US role in international affairs could erode US diplomacy and undermine institutions like NATO and the UN. That could have lasting effects on the geopolitical landscape, much as his first-term foreign policy decisions did.

Trump's isolationist first administration, briefly explained During his first term, from 2017 to 2021, Trump decided to withdraw the US from multiple international agreements, including the Joint Comprehensive Plan of Action (JCPOA), often called the Iran deal . That agreement, negotiated in 2015 under President Barack Obama, essentially eased US sanctions on Iran in exchange for curtailing its nuclear program and allowing greater international oversight of it.

"​The Iran deal was one of the worst and most one-sided transactions the United States has ever entered into," Trump said when the agreement was terminated in 2018. Since then, Iran has built up its stockpile of enriched uranium and increased its missile supply, reportedly bringing the program much closer to developing nuclear capabilities — despite the Trump administration's promise that Iran would never have them.

Trump also pulled the US out of the Paris climate agreement, which commits all signatories to reducing greenhouse gas emissions. Other diplomatic casualties of the Trump administration include the Intermediate-Range Nuclear Forces Treaty (INF), a Cold War-era pact between the US and Russia limiting the development of short- and intermediate-range nuclear weapons; the Open Skies Treaty , which allows signatories to conduct military reconnaissance fly-overs; and two international migration agreements .

Trump's first administration also saw him repeatedly critique NATO. He argued the other countries in the military alliance weren't spending enough on defense (and they did begin to spend more ), questioned whether the group was still necessary, and in 2020 withdrew almost 10,000 troops stationed in Germany , a decision Vice President Kamala Harris's foreign policy adviser Philip Gordon said seemed "designed to send a message about the limit of what Americans are prepared to spend to defend foreign borders and, more broadly, uphold world order."

What Trump could do in a second term In a second term, Trump has pledged to again withdraw from international agreements and organizations.

He explicitly promised to pull the US out of the Paris climate accords again , after the US re-entered the agreement under President Joe Biden. And he could limit US cooperation with UN organizations that his administration was critical of, like the World Health Organization . He has also floated a variety of new tariffs — at times calling for new taxes as high as 20 percent on US trading partners and recently threatening to impose tariffs of up to 100 percent on Mexico , the US's largest trading partner for goods in 2024 .

One partnership that would be difficult for Trump to alter is the US agreement with NATO. The NATO charter doesn't have a withdrawal mechanism. As Kavanagh explained, "Recently, Congress passed a law specifically aimed at NATO that would require congressional approval for withdrawal from NATO," in an effort to further protect the US membership in the alliance.

Even with that safeguard, there are ways a second Trump administration could hollow out NATO or other US military pacts, such as the one between the US, South Korea, and Japan meant to deter China and North Korea.

"​​Trump can decide to change US posture in any country, whether that's Asia or in Europe, and just pull forces out, close bases, stop investing in sort of the joint infrastructure and on all the committees and logistical pieces that keep an alliance running, that keep us tied into allies and partners," Kavanagh said. "Any president could do that."

But neglecting NATO and alienating those allies is not the only way a Trump administration could damage US foreign policy and diplomacy, according to James Lindsay, a senior fellow in US foreign policy at the Council on Foreign Relations.

"A lot is going to depend upon how he staffs his administration," Lindsay told Vox. "We don't have a good sense of who would be a Secretary of State, Secretary of Defense, [or] national security adviser." The people in those positions could have serious implications for all kinds of foreign policy decisions, from how (and if) ceasefire negotiations are conducted to which countries receive weapons transfers.

In the absence of a robust, experienced diplomatic apparatus, Trump may try to negotiate foreign policy largely on his own, as he has in the past. Those attempts had poor outcomes, like when his attempt to negotiate with North Korean leader Kim Jong Un ended in 2019 with no guarantees on the North Korean side to stop nuclear weapons development and no fundamental change in the relationship. His talks with the Taliban led to the withdrawal of US and NATO forces and the collapse of the civilian government in Afghanistan .

Trump has made big promises on the types of negotiations he'd conduct as president — like ending the war between Russia and Ukraine in 24 hours — but as was the case in his first term, the reality is likely to be much harder and messier than he's suggested.