Unrestricted submarine warfare refers to
germans attacking ships in american waters.

true
false

Germany's unrestricted submarine warfare was targeted primarily against British shipping, and it was in waters off the coast of Europe.

There was an effect on America, nevertheless.  Public outrage in the US against the Germans swept the nation following the sinking of the British ocean liner, Lusitania, which had happened in May, 1915.  When a German U-boat (submarine) sank the Lusitania, over 1,000 persons were killed, including more than 100 Americans. The passenger liner was targeted by the Germans because they suspected weapons were being shipped to Britain in the cargo hold of the ship.

Germany managed to stave off American entry into the war at the time by pledging to stop submarine attacks.  But two years later, the Germans resumed such attacks. This inflamed public opinion against Germany once again and poised America to go to war.