Transformed peacetime industries into war industries
Germany allied with Japan, Japan attacked America Germany had no choice and Hitler was not happy as he wanted to keep America out of the war.
At the start of the US involvement in WW II, the US was attacked by the Japanese. When the US declared that a state of war existed between the US and Japan, Germany declared war on the US. Your question should be was Germany justified in declaring war on the US.
There were several events leading up to the US calling for war against Germany. These included the Zimmerman Note, Germany announcing a policy of unrestricted submarine warfare, and the sinking of several American ships.
Japan is gaining very little after WW I China in civil war, encourages Japan to invade Left League of Nations Ally with Germany Invade China (not part of WW2) And then declaring war on the world with Germany and Italy
Germany's ally, Japan attacked the US naval base at Pearl Harbor, sinking the USS Arizona.
Because of the Japanese attack on Pearl Harbour in December 1941- Japan and Germany were allied by treaty, and the USA could not go to war against Japan without declaring war on Germany as well.
The immediate cause was Japan's attack on Pearl Harbor. This caused the US to declare war on Japan, which led to Germany and Italy declaring war on the US.
Declaring war on the USA after Japan declared war on America. Germany declared war on America hoping Japan would declare war on Russia. Since Japan did not declare war on Russia (Russia would later declare war on Japan), Germany did not have to declare on America. If Germany had not declared war on the USA, America would have difficulty in declaring war on Germany (although USA and Germany naval vessels in the North Atlantic were shooting at one another in 1941). If Germany had not declared war on the USA, then Hitler would not have had to face the military men and equipment of America. Although Russia fought the majority of land battles against Germany, it was American men and equipment that helped Russia and Britain and other Allied nations to defeat Germany.
The German telegram to Mexico and the sinking of U.S. merchant ships.
The Axis was composed of Germany, Italy, and Japan. FDR could not legally enter the war until the enemy country declared war on us. When Japan attacked Pearl Harbor, that was clearly a declaration of war by action, so FDR responded by declaring war on Japan verbally. Hitler then made the mistake of declaring war on the US verbally, so FDR responded by declaring war on Germany verbally. Mussolini also made the same mistake as Hitler, with the same result on Italy. Had Hitler and/or Mussolini not declared war on the US first, FDR could not have declared war on them and we could not have fought them.
Japan attacked the US without Germany even knowing about it. Germany declared war on the US on December 11, 1941. Japan probably didn't even know about that until it happened. Hitler had invaded Russia in 1941 and no doubt was hoping Japan would open a second front on the Russians as a favor for him declaring war on America.
AnswerThe USA had already given a huge amount of aid to the British and Soviet Union and was openly hostile to the ambitions of Germany. On an ideological level America was viewed as an inferior, racially mixed nation.Germany and Italy had signed a pact with Japan agreeing to cooperate in establishing a new order with Germany and Italy controlling Europe and Japan controlling East Asia.The pact also guaranteed support if any country attacked one of the Axis powers, technically once the USA had responded to the Japanese attack on Pearl Harbour by declaring war on Japan, Germany was bound to offer support to Japan.