Why did the US enter war late

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Germany’s resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson’s decision to lead the United States into World War l.

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The United States later declared war on German ally Austria-Hungary on December 7, 1917. Germany's resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson's decision to lead the United States into World War I.