How did germany's use of unrestricted submarine warfare lead to american entry into world war 1?

When the US ships carrying supplies etc to Britain, they were continuously sunk in European waters. In 1915, Germany declared unrestricted warfare on all ships which meant that they are able to sink any ship whether it be neutral or enemy. Due to the continual sinking of Neutral US assets, the people of the United States wanted to join the war, and thus in April of 1915, they joined their allies of the Commonwealth in the War effort