First of all, Americans wanted to stay "white", they did not wanted aliens to come and mix with their culture to produce an inferior race. "Many of these alien people are temperamentally and racially unfitted for easy assimilation" (Document F). In other words they were inferior to Americans, their race did not fit with the one of Americans. Also, they were not "temperamentally" capable to live in American society. "Thank God we have in America... the largest percentage of... pure unadulterated Anglo-Saxon stock; certainly the greatest of any nation in the Nordic breed" (Document I), said Ellison D. smith in 1924. Again in this phrase we can find Americans finding themselves superior to any other type of race. The same year in which the Immigration Act was passed Mr. Keaton from the Department of Adjutant of the American Legion of California wrote to John Raker in the House of Representatives in Washington, DC that he was "standing behing... 100 per cent in the fight to make this a white man's country" (Document G). Once again we can find proof that one of the most important reasons why the Immigration Act of 1924 was passed was because the United States wanted to have control over ethnicity.
Secondly, Congress had to study very well how would immigrants affect US economy. The United States Bureau of the Census shows a table from 1919 to 1925 showing national and personal income during those years. In here we can se the sharpest declines between 1920 and 1921. By 1924, the year in which the Immigration Act of 1924 was enforced, economy was getting better,