The Civil War!
[EDIT] No! The Civil War was fought in the U.S. from 1861-1865.
There were no U.S. wars fought in the decade of 1900-1909. The Spanish American War ended right before this decade began and World War One began in Europe in 1914. (We did not join World War One until 1918.) However, in this decade Russia and Japan were at war from 1904-1905.
1861-1865
The Union of the North, and the Confederates of the South fought in the US Civil War.
War of 1812
1860's
African Americans fought in the US Civil War, and they spoke out against slavery.
The Spanish American war was fought for independence for Cuba in the 1900's.
The Boxer Rebellion in China and the Philippine Insurrection from 1900 to 1902.
The US fought Germany and Japan in WWII. The US fought North Korea and Red China in the Korean War. The US fought Mexico in the Mexican War of 1846. The US fought Great Britain in the War of 1812. The US fought Spain in the Spanish-American War of 1898. The US fought Germany in WWI. The US fought North Vietnam during the Vietnam War. Is America at war with the nation of Iraq?
The Philippine Insurrection 1899-1902. As of the 21st Century, the name has been changed to "Philippine-American War." This war was bloodier than the Spanish-American War of 1898 which had spawned it.
The US has fought several wars.
Germany fought the us in world war 1
the worst war the USA. fought was the Civil War.
The North fought the South in the US Civil War.
in the Atlantic ocean.
no but they fought against Japan
World War II took place in the 20th century (1900s)
The US fought on the Allied, or UN side in Korea.