What two major event caused the u. s to abandon the policy of isolationiam?

The answers to this question are: Lusitania was bombed and sank and the
Zimmerman telegram.

Under President Woodrow Wilson, the United States was working on neutrality in the beginning of the First World War. Germans began using U boats in the Atlantic Ocean. The Atlantic Ocean was frequently used to transport passengers and cargo on British and US vessels. The German army bombed several ships and the Americans were killed. Nevertheless, the United States is still neutral and tried to negotiate with the Germans.

In 1915, Lusitania was bombed and sank. More than 1,000 passengers including over 100 Americans died. The US government continued its policy of maintaining neutrality and negotiating with Germans. Despite the anger of the United States, the pattern of negotiations following the bombardment continued. More and more ships were bombed in 1916 and 1917.

The final turning point was when the Zimmerman telegram was intercepted. Telegraph information revealed that Germans are trying to form an alliance with Mexico. If Mexico accepts an alliance invitation, they will be able to regain Arizona, Texas, New Mexico with the help of Germany. This information made Wilson change the mind about neutrality and the United States entered World War I in April 1917.