The united states entered the war because Germany was using submarines to sink our trading ships, they also sunk a passenger ship called the Lustitania, which killed many civilians. Another reason they entered war was because Germany sent the Zimmerman telegram that they sent to Mexico to try to have them enter the war against us. The telegram said that if they helped Germany, Germany would help them get land back that they lost during the <span>Mexican–American War</span>.
The purpose of the open door policy was to give all nations equal rights when trading with china.
Hitler gained support for anti-Jewish policies in Germany by blaming Jews for causing World War I, although he also blamed the Jews for losing the war, and for ill throughout the Great Depression.