yes they joined after Germany attacked the Lusitania.
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Actually, the US joined the Allies against Germany after the Zimmerman Telegram incidence. The sinking of the Lusitania inflamed US emotions, but it didn't directly lead to war with Germany. The Lusitania was sunk 7 May 1915 and the US didn't join the war until 1917.
America didn't fight in world war 1
Its World War 1 u idiot...
World War 1
america entered the war after pearl harbor
America's population at the beginning of world war 1 was considered mobilization. After World War One fifth of the world's population was infected.
world war 2
America didn't fight in World War 1!
America
none America didn't fight until world war 2
world war 1
America help provided heavy artillery for war and other war equipments.
America