Explain why the Palmer Raids took place in 1920. How did attitudes in the USA towards immigrants change during the years 1920 to 1929?

After the First World War ended, there were several political and social problems like wartime prisoners, drive for nationalism and the fear of socialism. The revolutionary challenge was tackled with twin tactics of reform and repression. As a result, the revolutionary challenge turned into bomb outrages in 1919. The anarchists, Bolsheviks and immigrants were blamed for the explosions. In one explosion the house of Palmer, the attorney general was damaged and to gain popularity for the coming elections, he ordered raids against the red threat i.e. increasing socialism. The offices of publishers, headquarters of socialist parties, private halls etc. were raided. Many Russian immigrants were deported and sent to jail. The famous case was of Sacco and Vanzetti in which they were accused of killing a postmaster but it finally came out that they were prosecuted because they were anarchists and immigrants.
Immigrants from eastern Europe were treated with hostility because they were Catholic Irish and Italians and orthodox and Jewish Russians, Poles and Hungarians. They felt their American way of life was in danger due to immigrants. In 1924, An Act was passed that limited the number of immigrants to 1,50,000 per year.