The allies were able to defeat Nazi Germany by deploying more soldiers, tanks, guns, ships, aircraft and supplies and also beating the Nazi German with their Mechanized warfare which was their forte.
The United States declared war against the Japanese on 11th December, 1941 which resulted in the declaration of the war against them by Nazi Germany in response to what the claimed was due to the nuisance caused by the United States government when the U.S. who was at the time neutral during the World War II.
The declaration was made by Adolf Hitler and on the same day, the United States. declared war also against the Nazi Germany.
The United States designated troops to Europe and Asia were they joined the Allies in defeating Nazi Germany and recovering conquered lands.
Hence, the significance of the involvement of the Unites States to the Allied victory in Europe was in the deployment of soldiers and recovery of conquered lands from the Nazi Germany.
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