United States of America

The United States of America (commonly referred to as the United States, the U.S., the USA, or America) is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to the east and Russia to the west across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country also possesses several territories in the Caribbean and Pacific.

The United States is the only nation to appear in all six Call of Duty games to date.

World War II (1940–1945)
The United States, effectively neutral during World War II's early stages after Nazi Germany's invasion of Poland in September 1939, began supplying materiel to the Allies in March 1941 through the Lend-Lease program. On December 7, 1941, the Empire of Japan launched a surprise attack on Pearl Harbor, prompting the United States to join the Allies against the Axis powers. Participation in the war spurred capital investment and industrial capacity. Among the major combatants, the United States was the only nation to become richer — indeed, far richer — instead of poorer because of the war. Allied conferences at Bretton Woods and Yalta outlined a new system of international organizations that placed the United States and Soviet Union at the center of world affairs. As victory was won in Europe, a 1945 international conference held in San Francisco produced the United Nations Charter, which became active after the war. The United States, having developed the first nuclear weapons, used them on the Japanese cities of Hiroshima and Nagasaki in August. Japan surrendered on September 2, ending the war.

World War II campaigns provide the setting for Call of Duty 1, 2, 3, and 5.

2011
The fictional plot of Call of Duty 4: Modern Warfare portrays the United States as having involved itself with Great Britain and Russian Loyalists in military actions to dissolve rebel activity in the Middle East and Russia during the Second Russian Civil War. After the execution of Yasir Al-Fulani, the country decides to send a multitude of Marines to locate the man responsible, Khaled Al-Asad. After failing to secure him, much of the United States' forces are wiped out by a nuclear attack, the first time a nuclear device would be used in warfare since World War II. Ironically, this attack was against the first and last country to use the weapon since. The United States, along with the United Kingdom and Russian Loyalist forces continue to pursue a campaign to find members of the rebels, killing three out of the four leaders or "Four Horsemen". The campaign is presumed to be continuing in Russia at the end of the game.

2016
In the plot for Call of Duty: Modern Warfare 2 the US, Britain, and several other countries form a group of elite soldiers that is currently called "Task Force 141", lead by Captain "Soap" MacTavish, with other notable members being Ghost and "Roach" Sanderson.

The United States appears to still be embroiled in Afghanistan as the 1st Battalion, 75th Ranger Regiment is in country at the beginning of events of Modern Warfare 2. The events in No Russian, committed by Vladimir Makarov and his group of Ultranationalists (including undercover Ranger Joseph Allen aka Alexei Borodin), stir public outrage against the United States when Makarov kills Joseph Allen to successfully portray the bloodbath as an American-backed terrorist action.

The United States itself is then invaded by Russia, triggering a devastating war in which Washington DC and the surrounding area becomes the battlefield. Civilians and other key personnel are evacuated from the DC area (via the Washington Monument) while the military attempts to retake the city.

During the siege of the American East Coast, Task Force 141 along with the American 6th fleet are sent on the offensive. Their task is to disable SAM sites on oil rigs for the inevitable assault on the Russian mainland to retrieve Prisoner 627 from a gulag on the Kamchatka Peninsula. Afterwards, Task Force 141 and the rest of the supporting American forces, go on actions to locate and kill Makarov.

After the events of Of Their Own Accord and Second Sun, the detonation of a nuclear weapon in the atmosphere above Washington DC causes an EMP wave the city and surrounding areas, which disables all electronics and equipment. This enables the US military to eventually take back control of Washington DC from the overwhelming amount of Russian vehicles and troops.

However, it is later revealed that General Shepherd engineered the entire war in order to rise to glory as the man who wiped out terrorism, as well as ensure there were never any shortage of volunteers in the US military. After killing Roach and Ghost, he was tracked down by Soap and Price. After a battle and an exchange of fists with Price, he was killed by Soap, who threw a knife into his eye.

It is unclear what role the United States takes after the plot of Modern Warfare 2, though it is presumed that with Russian forces defeated on the home front, a campaign aimed at the Russian mainland would follow.