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The country who helped the Allies win WW2 was the USA. Later on in the war, the dropping of the atomic bomb in Pearl Harbor by the Japanese, president Franklin D. Roosevelt declared war on Japan. Then the USA joined the Allies ,with the battle of D-Day, and defeated the German Nazis. The US left the war a little earlier before the actual ending of WW2. If it weren't for the US, the Allies would have lost to the Axis.

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16y ago

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