Question: when did united states enter world war i?
Answer: April 1917

The American entry into World War I came in April 1917 , after more than two and a half years of efforts by President Woodrow Wilson to keep the United States out of the war . Apart from an Anglophile element urging early support for the British , American public opinion reflected that of the president : the sentiment for neutrality was particularly strong among Irish Americans , German Americans and Scandinavian Americans , as well as among church leaders and among women in general . On the other hand , even before World War I had broken out , American opinion had been more negative toward Germany than towards any other country in Europe . Over time , especially after reports of atrocities in Belgium in 1914 and following the sinking of the passenger liner RMS Lusitania in 1915 , the American people increasingly came to see Germany as the aggressor in Europe .