There's stupid now
A short list of undeclared wars
First Barbary War (1805)
Algerian War (1815)
First Sumatran Expedition (1832)
Cayuse War (1847)
First Fiji Expedition (1855)
Second Opium War (1856)
Paraguay Expedition (1859)
Formosa Expedition (1867)
Korean Expedition (1871)
Second Samoan Civil War (1898)
Moro Rebellion (1899)
Boxer Rebellion (1900)
Nicaraguan Campaign (1912)
Mexican Revolution (1914)
Occupation of Haiti (1915)
Occupation of Dominican Republic (1916)
Cold War-- Includes wars with USSR, Grenada, Dominican Republic, Congo, Cambodia, Laos, Vietnam, Cuba, Indochina, Czechoslovakia, and Korea. (1947)
Puerto Rican Nationalist Revolts (1950)
First Gulf of Sidra Incident (1981)
Lebanese Civil War (1982)
Bombing of Libya (1986)
Iran-Iraq War (1987)
Invasion of Panama (1989)
First Gulf War (1990)
Somali Civil War (1992)
Bosnian War (1993)
Operation Uphold Democracy--Haiti (1994)
Bombings of Afghanistan and Sudan (1998)
Kosovo War (1999)
War on Terror-- Wars with Iraq, Afghanistan, the Philippines, Somalia, Pakistan, and Yemen. (2001)
Second Liberian War (2003)
Lord's Resistance Army Insurgency--Sudan (2011)
Libyan Civil War (2011)