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.
Back then it was justified by the citizens of the U.S. because they were afraid of communists and they hated communism. It was an injustice for The U.S. to enter the Vietnam War.
They were attacked on US soil.
The main sparks of the United States involvement in World War 1 was the assasination of the Archduke and the sinking of the Lusitania.
The perspective was that the war was justified since we were attacked.
Self defense, the US was attacked.
Supplying Allies with weapons
The Japanesse surrender.
sinking of lusitania
they had sexual inter corse
The US is not yet involved in world 11. The next world war should be WWIII so they have a way to go.
The United States wasn't at war with Japan in WW1.
World War 2 was the only war with US involvement that didn't involve a large, organized dissent movement. Pearl Harbor was evidence that an 'isolationist' stance was untenable. As knowledge of fascist and Nazi atrocities increased, more and more of the US population saw that US involvement was defendable. See link.
The US began it's involvement in WW2 on December 8, 1941.The day after the attack on Pearl Harbor.
December 7th 1941
The US paid for the costs of its involvement in World War 1 by using up 52 percent of its GNP during that period for war expenses. Its belated entry into the war however helped prevent a worse post war recession .
Almost every American wanted American involvement in World War Two after the attack on Pearl Harbor.