In September and October 2020, Kosovo, Serbia, the United Arab Emirates (UAE), Bahrain, and Sudan normalized relations with Israel in a flurry of agreements brokered by the United States. President Donald Trump suggested that, in addition to being valuable on their own terms, the agreements were part of a broader diplomatic effort to pressure the Palestinians into negotiating a peace deal with Israel. In December, the White House announced normalization of relations between Israel and Morocco in apparent exchange for U.S. recognition of Moroccan sovereignty over the disputed territory of Western Sahara.

On September 15, 2020, a World Trade Organization (WTO) panel ruled that certain tariffs the United States imposed on Chinese products violated Articles I (most-favored-nation) and II (tariff bindings) of the General Agreement on Tariffs and Trade (GATT). The panel rejected the U.S. attempt to invoke a “public morals” defense pursuant to GATT Article XX, holding that although countries receive substantial deference in defining “public morals,” the United States failed to prove that the tariffs were necessary to achieve its stated public morals objective.

On October 3, 2019, the United States and the United Kingdom reached a bilateral agreement to facilitate more efficient data access between the two countries for law enforcement purposes. The Agreement on Access to Electronic Data for the Purpose of Countering Serious Crime (U.S.-UK Data Access Agreement) was signed by U.S. Attorney General William Barr and UK Home Secretary Priti Patel. This is the first such agreement made by the United States after the passage of the 2018 Clarifying Lawful Overseas Use of Data (CLOUD) Act, which authorizes and structures future bilateral agreements on data sharing. Pursuant to the CLOUD Act, Congress has 180 days following receipt of a notification regarding the U.S.-UK Data Access Agreement to block its entry into force via a joint resolution, which would require a majority vote in both houses of Congress and either presidential signature or a subsequent congressional override of a presidential veto.

The Trump administration is engaged in an ongoing legal battle against the makers of two Chinese smartphone applications, TikTok and WeChat, over their data-collection and content moderation practices. The administration has used both the International Emergency Economic Powers Act (IEEPA) and the Committee on Foreign Investment in the United States (CFIUS) in an attempt to force the companies to cease U.S. operations and, in TikTok's case, to change ownership. The administration's actions have spurred multiple legal challenges, several of which are ongoing, and for now, both TikTok and WeChat remain in operation in the United States.

On September 25, 2019, the Third Extraordinary Congress of the Universal Postal Union (UPU) adopted a proposal on terminal dues rates—a decision that led the United States to remain a member state. The United States had given its one-year notice of withdrawal from the UPU eleven months earlier, citing concerns that the existing system unfairly advantaged certain developing nations, including China. Following the UPU's decision, the United States rescinded its notice of withdrawal. Under the new system, the United States can begin self-posting terminal dues rates in July 2020.

In June 2019, protests erupted in Hong Kong after its government proposed an extradition agreement with mainland China. Alarmed by the protests, the Central Committee of the Chinese Communist Party announced that it would consider new national security measures for Hong Kong. On June 30, 2020, China's National People's Congress Standing Committee (NPCSC) passed the “Law of the People's Republic of China on Safeguarding National Security in the Hong Kong Special Administrative Region.” While the law was under consideration, the United States responded by declaring that Hong Kong was no longer significantly autonomous from mainland China and beginning the process of ending Hong Kong's special status under U.S. law. The United States and its allies continue to criticize Hong Kong's deteriorating autonomy from China, pointing to the postponement of elections in Hong Kong as further evidence.

On November 4, 2019, the Trump administration notified the United Nations that the United States was withdrawing from the Paris Agreement, prompting expressions of regret from a number of countries. Although President Trump had announced in June 2017 that the United States intended to withdraw from the Paris Agreement, its terms had prevented the United States from giving formal notice of withdrawal until November 4, 2019. The withdrawal will take effect on November 4, 2020. Domestically, the governors of many U.S. states responded to the withdrawal by reaffirming their commitment to the goals of the Paris Agreement, consistent with recurring tensions between the Trump administration and progressive states with respect to climate. In another major manifestation of these tensions, on October 23, 2019, the United States sued California over the state's cap-and-trade agreement with Quebec, Canada, alleging that this agreement is an unconstitutional exercise of foreign affairs powers.

In the fall of 2019, the Trump administration reached several trade arrangements, some of them tentative, with important U.S. trade partners. On October 11, 2019, China and the United States announced a preliminary trade deal subject to finalization—one that came after more than a year of escalating tariffs. Just a week earlier, the United States had signed two trade agreements with Japan, one regarding tariff reductions and the other regarding digital trade. None of these deals appear to require subsequent congressional approval in the eyes of the executive branch, unlike the earlier United States-Mexico-Canada-Agreement (USMCA), which was signed in November 2018 and whose fate in Congress appears promising as of mid-December of 2019. In addition to these trade arrangements, the fall of 2019 saw several developments in trade relations between the United States and the European Union tied to the long-running trade disputes.

On September 2, 2020, the Trump administration announced that the United States had added the International Criminal Court (ICC) prosecutor, Fatou Bensouda, and the head of the Office of the Prosecutor's Jurisdiction, Complementarity, and Cooperation Division, Phakiso Mochochoko, to the Treasury Department's Office of Foreign Assets Control List of Specially Designated Nationals and Blocked Persons. The action followed Executive Order 13,928, signed in June, which authorized economic sanctions and visa restrictions on ICC employees who are investigating whether U.S. forces committed war crimes in Afghanistan. Governments and human rights groups decried the sanctions as an attack on international justice.

The United States withdrew from the Joint Comprehensive Plan of Action (JCPOA) on May 8, 2018, and subsequently reimposed a range of unilateral sanctions on Iran. Throughout mid-2020, the Trump administration sought multilateral support for renewed UN sanctions against Iran, but the Security Council rejected those efforts. In response, the administration moved to initiate snapback sanctions under the terms of the JCPOA and UN Security Council Resolution 2231. However, JCPOA participants and the Security Council largely rebuffed the administration's contention that it could activate the snapback mechanism, instead taking the position that U.S. withdrawal from the JCPOA means that it is no longer a “participant state” as required to invoke snapback sanctions.

Political instability and violence escalated in northeastern Syria in October 2019, following President Trump's decision to withdraw most U.S. troops from the country. Trump's decision left U.S.-backed Kurdish forces vulnerable to attacks by Turkey, intensifying an already dire humanitarian situation. Soon thereafter, Kurdish leaders negotiated an agreement with the Russian-backed Syrian government to fill the vacuum left by the U.S. withdrawal. By late October, the president of Turkey agreed to a ceasefire in response to diplomatic and economic pressure from the United States and to the arrival of Russian and Syrian troops into northeastern Syria. Shortly thereafter, U.S. forces carried out a raid in northwestern Syria that resulted in the death of the leader of the Islamic State of Iraq and the Levant (ISIL)—a raid that relied in part on intelligence gathered earlier by Kurdish allies.

Longstanding tensions between Congress and the executive over U.S. support to the Saudi-led coalition in Yemen have spurred conflict between the branches over arms sales. In May 2019, U.S. Secretary of State Michael Pompeo declared an emergency under the Arms Export Control Act (AECA) to bypass congressional “freezes” on arms sales and complete $8.1 billion in sales to members of the Saudi-led coalition. In response, Congress requested that the State Department inspector general (IG) investigate the matter. In a report released in August 2020, the IG determined that the emergency declaration comported with the AECA's procedural requirements but that the State Department's risk assessments and civilian casualty mitigation measures did not fully address legal concerns about the sales. The Trump administration has continued to move forward with arms sales, including by unilaterally reinterpreting a nonbinding multilateral export control regime to eliminate prohibitions on the export of certain unmanned aerial systems (UAS). A bipartisan group of legislators has introduced a bill to prevent such sales to all countries except select U.S. allies. In September, a UN report criticized U.S. and other countries’ arms sales to the Saudi-led coalition and recommended referral of the situation in Yemen to the International Criminal Court (ICC).