The sink of Lusitania which killed nearly 128 Americans put of 1200 was strong enough to convince Americans to intervention.
Step-by-step explanation:
In the 18th century, America was a ground for many immigrants and indeed Americans made use out of it. When the war began in the year 1914, Americans automatically starting shipping raw materials and goods to other country.
However, the sink of Lusitania which killed nearly 128 Americans put of 1200 was strong enough to convince Americans to intervention. This cause affected the connection between Washington and Berlin and resulted the people against Germany.
1916, American army got into Mexico, with the National Defense Act extended the army and soon on 2nd April, 1317 America declared war against Germany.