It was not a war, it was the attack on Pearl Harbor, unless you're thinking of when the US joined World War 2 the day following the attack on Pearl Harbor.
The United States Senate declared war against Japan and later Germany during World War II in 1941.
The United States declared war on Japan December 8 , 1941 .
In December 7 1941
Argentina, Bolivia, Brazil, Costa Rica, Cuba, Dominion Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Paraguay, Peru, Uruguay& Venezuela all declared war on Germany.Also involved was Chile who declared war on Japan in March 1945 and Columbia who never officially declared war but a "State of Belligerence" did exist with Germany.Costa Rica declared war Japan on December 8th, 1941 and Germany and Italy shortly afterwards.Cuba declared war of Japan on December 8th, 1941 and Germany and Italy on December 11th, 1941.Nicaragua declared war on Japan on December 8th, 1941 and Germany and Italy on December 11th, 1941.El Salvador declared war on Japan on December 8th, 1941 and Germany on December 12th,1941.Haiti declared war on Japan on December 8th, 1941 and Germany and Italy a few days later.Honduras declared war on Japan on December 8th, 1941 and Germany and Italy on December 13th.Guatemala declared war on Japan on December 9th, 1941 and Germany on December 12th, 1941.Dominion Republic declared war on Japan after the attacks on pearl harbour and on Germany and Italy after they declared war on the USA.Mexico declared war on Germany, Italy and Japan on May 22nd, 1942.Brazil declared war on Germany and Italy on August 22nd, 1942.Bolivia declared war on Germany on April 7th, 1943.Ecuador declared war on Germany on January 2nd, 1945.Paraguay declared war on Germany on February 2nd, 1945.Uruguay declared war on Germany, Italy and Japan on February 8th, 1945.Argentina declared war on Germany and Japan on March 27th, 1945.Both Peru and Venezuela declared war on Germany in 1945.
December 8 1941
The US .
December 7th, 1941
On December 8, 1941 President Roosevelt declared war on Japan. He stated all the places that the Japanese had attacked on the previous day: the day that will remain infamous, the day of the attack on Pearl Harbor.
after. December 7th 1941
December 8, 1941.
Pearl Harbor was attacked December 7th 1941. Congress then declared war on Japan December 8th 1941.
They declared war on the US- 11 Dec 1941
Germany declared war on the US on December 11th.AnswerThey didn't. Germany and Italy declared war on America, after the Japanese bombed Pearl Harbour.AnswerDecember 8th, 1941