The majority of nation-building attempts in the 20th century failed, including efforts in Africa, Latin America, and Asia. The most successful examples of nation-building were post - World War II Germany and Japan. Both countries had economies that had been ruined by the war and faced significant political and social upheavals. The successful instances of nation-building required substantial economic aid and a long-term military presence.

Post–Cold War nation-building efforts by the United States largely failed. The Somalia intervention and the Haiti interventions were examples of unsuccessful initiatives. In Somalia, outside powers were unable to establish stability or ensure security. Somalia remained a failed state where greater stability existed in the breakaway provinces of Somaliland and Puntland (neither of which had international diplomatic recognition because of concerns by the global community that their independence could lead to the complete collapse of Somalia). In Haiti, political instability, including successive coups, led to continued social and economic strife, despite Americanand United Nations (UN) - led operations to restore order.

The multilateral effort at nation-building in Bosnia was more successful. Following the Dayton Accords, a North Atlantic Treaty Organization (NATO) - led (and later European Union (EU) - commanded) peacekeeping mission provided a secure environment for economic and political development. There were multilateral military missions in Bosnia for more than 10 years, and the country received significant economic assistance from the EU and the United States. Bosnia reinforced the lessons of Germany and Japan.

U.S.-led nation-building in Afghanistan and Iraq has had mixed results. After the Afghanistan intervention, the United States employed a three-pronged nation-building strategy. First, political power was concentrated in the hands of an interim government led by Hamid Karzai (Karzai enjoyed the support of the main political and ethnic factions in Afghanistan and subsequently won presidential elections). Second, political and economic recovery was overseen by the UN, and later by NATO. Third, American forces continued to undertake security operations. Substantial progress in Afghanistan was undermined by a continuing insurgency by the Taliban and Al Qaeda, as well as the limited scope of reconstruction efforts (initially, there were only 12 regional reconstruction teams deployed outside of Kabul). It was estimated that Afghanistan needed $10 billion over a five-year period to rebuild its economy and restore its civil society. The United States and other countries also failed to provide adequate financial aid. International donors provided $4.5 billion over a five-year span, with the United States providing the largest share. Countries such as Saudi Arabia, Japan, and Australia provided far less in assistance than they had initially pledged.

Following the Iraq War, the United States failed to put in place a post - Saddam Hussein government that enjoyed popular support, although subsequent balloting established a democratically elected parliament and government. In addition, the U.S.-led coalition failed to constrain an ongoing insurgency that undermined political and social stability and prevented economic development. The insurgency weakened aid efforts, as the instability caused international organizations to withdraw staff and curtail programs. Nonetheless, U.S. efforts to provide economic assistance had some notable successes. At a November 2004 conference, international donors agreed to write off 80 percent of Iraq's $120 billion foreign debt. The effort at debt reduction was led by former secretary of state James A. Baker III and followed the American cancellation of 100 percent of Iraq's $4 billion debt to the United States.