Contemporary history

After the Cold War, the conflict in the Middle East triggered a crisis in 1990, when Iraq under Sadaam Hussein invaded and attempted to annex Kuwait, an ally of the United States. Fearing that the instability would spread to other regions, President George H.W. Bush launched Operation Desert Shield, a defensive force buildup in Saudi Arabia, and Operation Desert Storm, in a staging titled the Gulf War; waged by coalition forces from 34 nations, led by the United States against Iraq ending in the successful expulsion of Iraqi forces from Kuwait, restoring the former monarchy.

Originating in U.S. defense networks, the Internet spread to international academic networks, and then to the public in the 1990s, greatly affecting the global economy, society, and culture.

Due to the dot-com boom, stable monetary policy under Alan Greenspan, and reduced social welfare spending, the 1990s saw the longest economic expansion in modern U.S. history, ending in 2001. Beginning in 1994, the U.S. entered into the North American Free Trade Agreement (NAFTA), linking 450 million people producing $17 trillion worth of goods and services. The goal of the agreement was to eliminate trade and investment barriers among the U.S., Canada, and Mexico by January 1, 2008. Trade among the three partners has soared since NAFTA went into force.

On September 11, 2001, Al-Qaeda terrorists struck the World Trade Center in New York City and the Pentagon near Washington, D.C., killing nearly 3,000 people.In response, the United States launched the War on Terror, which included war in Afghanistan and the 2003–11 Iraq War.In 2007, the Bush administration ordered a major troop surge in the Iraq War, which successfully reduced violence and led to greater stability in the region.

Government policy designed to promote affordable housing, widespread failures in corporate and regulatory governance,and historically low interest rates set by the Federal Reserve led to the mid-2000s housing bubble, which culminated with the 2008 financial crisis, the largest economic contraction in the nation's history since the Great Depression. Barack Obama, the first African American and multiracial president, was elected in 2008 amid the crisis, and subsequently passed stimulus measures and the Dodd-Frank Wall Street Reform and Consumer Protection Act in an attempt to mitigate its negative effects and ensure there would not be a repeat of the crisis. The stimulus facilitated infrastructure improvements and a relative decline in unemployment. Dodd-Frank improved financial stability and consumer protection, although there is evidence it may have had a negative impact on small banks.

In 2010, the Obama administration passed the Affordable Care Act, which made the most sweeping reforms to the nation's healthcare system in nearly five decades, including mandates, subsidies and insurance exchanges. The law caused a significant reduction in the number and percentage of people without health insurance, with 24 million covered during 2016, but remains controversial due to its impact on healthcare costs, insurance premiums, and economic performance. Although the recession reached its trough in June 2009, voters remained frustrated with the slow pace of the economic recovery. The Republicans, who stood in opposition to Obama's policies, won control of the House of Representatives with a landslide in 2010 and control of the Senate in 2014.

American forces in Iraq were withdrawn in large numbers in 2009 and 2010, and the war in the region was declared formally over in December 2011. The withdrawal caused an escalation of sectarian insurgency, leading to the rise of the Islamic State of Iraq and the Levant, the successor of al-Qaeda in the region. In 2014, Obama announced a restoration of full diplomatic relations with Cuba for the first time since 1961. The next year, the United States as a member of the P5+1 countries signed the Joint Comprehensive Plan of Action, an agreement aimed to slow the development of Iran's nuclear program.