Foreign relations and military

The United States exercises global economic, political, and military influence. It is a permanent member of the United Nations Security Council and New York City hosts the United Nations Headquarters. Almost all countries have embassies in Washington, D.C., and many host consulates around the country. Likewise, nearly all nations host American diplomatic missions. However, Cuba, Iran, North Korea, Bhutan, Sudan, and the Republic of China (Taiwan) do not have formal diplomatic relations with the United States.

The United States enjoys a special relationship with the United Kingdom and strong ties with Australia, New Zealand, Japan, Israel, and fellow NATO members. It also works closely with its neighbors through the Organization of American States and free trade agreements such as the trilateral North American Free Trade Agreement with Canada and Mexico. In 2005, the United States spent $27 billion on official development assistance, the most in the world. However, as a share of gross national income (GNI), the U.S. contribution of 0.22% ranked twentieth of twenty-two donor states. Nongovernmental sources such as private foundations, corporations, and educational and religious institutions donated $96 billion. The combined total of $123 billion is also the most in the world and seventh as a percentage of GNI.The president holds the title of commander-in-chief of the nation's armed forces and appoints its leaders, the secretary of defense and the Joint Chiefs of Staff. The United States Department of Defense administers the armed forces, including the Army, Navy, Marine Corps, and Air Force. The Coast Guard is run by the Department of Homeland Security in peacetime and the Department of the Navy in time of war. In 2005, the military had 1.38 million personnel on active duty,along with several hundred thousand each in the Reserves and the National Guard for a total of 2.3 million troops. The Department of Defense also employs about 700,000 civilians, not including contractors. Military service is voluntary, though conscription may occur in wartime through the Selective Service System. American forces can be rapidly deployed by the Air Force's large fleet of transport aircraft and aerial refueling tankers, the Navy's fleet of eleven active aircraft carriers, and Marine Expeditionary Units at sea in the Navy's Atlantic and Pacific fleets. Outside of the United States, the military is deployed to 770 bases and facilities, on every continent except Antarctica. The extent of this global military presence has prompted some scholars to describe the United States as maintaining an "empire of bases."

Total U.S. military spending in 2006, over $528 billion, was 46% of global military spending and greater than the next fourteen largest national military expenditures combined. (In purchasing power parity terms, it was larger than the next six such expenditures combined.) The per capita spending of $1,756 was about ten times the world average. At 4.06% of GDP, U.S. military spending is ranked 27th out of 172 nations. The proposed base Department of Defense budget for 2009, $515.4 billion, is a 7% increase over 2008 and a nearly 74% increase over 2001. The cost of the Iraq War to the United States has been estimated to reach $2.7 trillion. As of May 3, 2009, the United States had suffered 4,284 military fatalities during the war and over 31,000 wounded.