United States of America
US · North America · NATO founding member · UN Security Council permanent member (P5)
The United States is the world’s largest economy and largest defence spender, maintaining a network of approximately 750 military bases and facilities across more than 80 countries. It holds a permanent seat on the UN Security Council with veto power and is the dominant state in NATO, contributing roughly 70% of the alliance’s combined defence expenditure.
Since 1991, US foreign policy has been defined by a debate between liberal internationalism — maintaining the rules-based order through alliances and institutions — and various forms of retrenchment or restraint. The Trump administration’s return to power in 2025 has shifted the balance sharply toward unilateralism and transactional bilateralism.
The US is a treaty ally with over 50 states, including formal defence commitments to Japan, South Korea, Australia, and all 31 other NATO members under Article 5 (32 total in the alliance). The reliability of these commitments has been questioned under the current administration, creating significant alliance management challenges particularly in Europe and the Indo-Pacific.
The US defence budget for FY2024 was approximately $886 billion under the National Defense Authorization Act (NDAA). SIPRI’s broader military expenditure calculation — which includes veterans’ affairs and off-budget defence items — tracks closer to $968–997 billion for 2024, accounting for roughly 40% of global military expenditure (SIPRI, 2024). Active military personnel number approximately 1.3 million, with 800,000 reserve forces. The US maintains the world’s most powerful naval force, with 11 nuclear-powered aircraft carrier strike groups.
The US is one of five recognised nuclear weapon states under the Non-Proliferation Treaty (NPT) and maintains an estimated 5,550 nuclear warheads, of which approximately 1,700 are deployed (Federation of American Scientists, 2024). It provides extended nuclear deterrence guarantees (“nuclear umbrella”) to NATO allies, Japan, South Korea, and Australia.
China: Strategic competition across trade, technology, Taiwan, and the South China Sea. The US maintains “strategic ambiguity” on Taiwan under the Taiwan Relations Act (1979), selling arms but not formally committing to military defence.
Russia: The US has provided substantial military and financial assistance to Ukraine since Russia’s 2022 invasion. Relations are at their lowest point since the Cold War.
Iran: No formal diplomatic relations since 1980. The US has designated Iran’s Islamic Revolutionary Guard Corps as a foreign terrorist organisation and maintains extensive sanctions under multiple legal authorities.
NATO burden-sharing: The Trump administration has demanded allies reach 5% of GDP in defence spending, creating significant tension with European partners.
Realists such as John Mearsheimer argue the US should pursue “offshore balancing” — retrenching from expensive overseas commitments and relying on regional powers to manage local threats. Liberal internationalists (Ikenberry) counter that the rules-based order the US built benefits American interests by reducing the costs of coordination. The current administration’s behaviour fits neither cleanly: it is neither offshore balancing nor liberal hegemony, but a form of Jacksonian transactionalism that treats alliances as commercial arrangements rather than strategic commitments.
- 1NATO, Defence Expenditure of NATO Countries (2014–2024) — nato.int
- 2SIPRI, Military Expenditure Database 2024 — sipri.org
- 3Federation of American Scientists, Status of World Nuclear Forces — fas.org
- 4IMF, World Economic Outlook Database 2024 — imf.org
- 5US Department of State, Taiwan Relations Act (1979) — state.gov