The united states tried to avoid involvement in world war 1 by following a policy of

neutrality

As the war in Europe erupted in 1914, the President of the United States, Woodrow Wilson, proclaimed an official policy of neutrality in regard to the war.  That policy was hard to maintain, however, because the warring parties in Europe were battling over the seas and this affected shipping coming from the United States.  Britain had blockaded Germany, and the Germans had responded by launching submarine (U-boat) warfare against vessels coming to deliver supplies to Britain.  When the passenger liner Lusitania was sunk by the Germans in 1915, killing over 1,000 people including 120 Americans, the USA was almost drawn into the war at that point.