In July, the United States, the North Atlantic Treaty Organization (NATO), the European Union (EU), and other allies attributed a variety of malicious cyber activities, including the Microsoft Exchange hack, to China. This joint attribution builds on commitments made in June summits with NATO, the G7, the EU, and the United Kingdom, and is consistent with the Biden administration's multilateral approach to confronting cybersecurity threats and China more generally. Still, critics question whether the administration's efforts will succeed in altering the behavior of states that pose cybersecurity threats to the United States.

On May 23, 2021, Belarusian authorities forced a Ryanair flight from Athens, Greece to Vilnius, Lithuania to land in Minsk in response to a false bomb threat and then arrested Roman Protasevich, an exiled journalist onboard the flight. The United States joined much of the international community in condemning the flight's diversion and imposing additional sanctions on Belarusian President Alexander Lukashenko's regime, adding to those levied throughout the last year due to Lukashenko's repression of opposition figures and others who have protested the results of the August 2020 Belarusian election.

On April 1, 2021, the Biden administration issued an executive order reversing the Trump administration's sanctions on International Criminal Court (ICC) personnel. The administration rescinded the sanctions placed upon the ICC prosecutor, Fatou Bensouda, and the head of the Office of the Prosecutor's Jurisdiction, Complementarity, and Cooperation Division, Phakiso Mochochoko, and removed the officials from the Treasury Department's Office of Foreign Assets Control List of Specially Designated Nationals and Blocked Persons. The ICC, European Union (EU), and human rights groups welcomed the reversal.

As the COVID-19 pandemic continues to rage across the world, the United States and its allies are pushing for answers about the virus's origins while China rebuffs inquiry into its early handling of the outbreak. Meanwhile, a growing U.S. stockpile of vaccines has opened new avenues for “vaccine diplomacy,” and the Biden administration has thrown its weight behind an effort to suspend cross-border intellectual property (IP) rules for vaccine manufacturing. In the near term, however, experts expect vaccination rates and access will continue to vary widely between countries depending on their wealth.

In Nestlé USA, Inc. v. Doe, et al., former child slaves who were trafficked into Côte d'Ivoire to work on cocoa farms filed suit under the Alien Tort Statute (ATS) against U.S.-based companies that purchase cocoa from and provide other support to the farms, alleging that the companies aided and abetted child slavery. By an 8–1 vote, the Supreme Court held that the case involved an impermissible extraterritorial application of the ATS under the Court's precedent in Kiobel. The Court declined to resolve whether domestic corporations may be held liable under the ATS, although five justices across several opinions expressed the view that such corporations are not immune from ATS suits. The question of whether the Court should ever create new causes of action under the ATS prompted significant debate, with three justices suggesting that they would overrule Sosa v. Álvarez-Machain and a fourth indicating that there are strong arguments to reject judicial creation of any new ATS causes of action.

Nearly twenty years after the U.S. military began operations against the Taliban in Afghanistan, President Joseph R. Biden reported on August 31, 2021, that the last U.S. combat troops had departed the country. Biden announced on April 14, 2021, that the United States would withdraw combat troops from Afghanistan before the twenty-year anniversary of September 11, 2001, and NATO member states decided to depart the country simultaneously. The withdrawal followed an early 2020 deal between the Taliban and the Trump administration, which conditioned the pullout on Taliban agreement not to harbor terrorists that target the United States and its allies. Over the course of a week and a half in mid-August, the Taliban captured most of Afghanistan's provincial capitals, entering Kabul on August 15. The Afghan government collapsed, and President Ashraf Ghani fled the country. Through the end of August, the United States and other countries conducted a major airlift operation to evacuate their nationals and Afghans considered at risk of Taliban reprisals, though many were left behind amid risks of renewed civil war and humanitarian crisis.

On June 1, 2020, the Supreme Court unanimously held that the Convention on the Recognition and Enforcement of Foreign Arbitral Awards (New York Convention or Convention) does not conflict with domestic equitable estoppel doctrines that permit the enforcement of arbitration agreements by nonsignatories. The Court interpreted the text of the Convention as being silent on the issue of enforcement by nonsignatories and thus leaving this issue to domestic law. The Court noted that some postratification practice (including the recommendation of a UN commission) and the views of the executive branch were consistent with its conclusion, but it did not determine how much weight should be accorded to these sources.

In Opati v. Republic of Sudan, the Supreme Court upheld a $4.3 billion award of punitive damages against Sudan for its support of the 1998 bombings of U.S. embassies in Kenya and Tanzania. The Supreme Court held that Congress's 2008 amendments to the Foreign Sovereign Immunities Act (FSIA) authorized the plaintiffs to recover punitive damages from state sponsors of terrorism for acts committed prior to the enactment of these amendments. This case is part of a broader trend of U.S. litigation brought against states who are designated sponsors of terrorism or alternatively are deemed responsible for acts of terrorism within the United States.

President Trump decided in mid-April of 2020 to suspend U.S. funding for the World Health Organization (WHO) and to have his administration review its performance, contending that it was biased in favor of China and inept in its handling of the COVID-19 pandemic. In a letter to the WHO director-general a month later, Trump informed the director-general that his administration's review confirmed his accusations. He threatened that, unless the WHO implemented significant reforms, the United States would reconsider its membership in the organization. Less than two weeks later, on May 29, 2020, Trump announced his decision to terminate the U.S. relationship with the WHO. On July 6, the administration gave formal notice of U.S. withdrawal to the UN secretary-general, the depositary for the WHO Constitution. Assuming certain legal preconditions are satisfied and the notice of withdrawal is not revoked, the withdrawal will take effect on July 6, 2021.

On November 30, 2018, Canada, Mexico, and the United States signed an agreement renegotiating the North American Free Trade Agreement (NAFTA). By the spring of 2020, all three countries had approved this agreement—known in the United States as the United States-Mexico-Canada Agreement (USMCA)—through their respective domestic ratification processes. The USMCA entered into force on July 1, 2020, amid extended U.S.-Mexico and U.S.-Canada border restrictions due to the COVID-19 pandemic. On August 6, 2020, President Trump imposed tariffs on Canadian aluminum—tariffs that his administration had previously put in place in 2018 but had removed in 2019 in order to smooth the USMCA's path to ratification.

In the spring of 2020, the Appeals Chamber of the International Criminal Court (ICC) authorized the ICC's prosecutor to investigate alleged international crimes committed in Afghanistan. The Trump administration strongly condemned this decision. In an escalation of retaliatory measures against the ICC, President Trump signed an executive order authorizing economic sanctions against foreign persons involved in the investigation and visa restrictions against those persons and their immediate family members. The ICC described these actions as a threat to the rule of law.