This thesis studies events that preceded America's entries into the First and Second World Wars to discover similarities and dissimilarities. Comparing America's entries into the World Wars provides an insight into major events that influenced future ones and changed America. Research was conducted from primary sources of Presidents Woodrow Wilson and Franklin D. Roosevelt. In addition, secondary sources were used that study the events preceding America's entries into World War I and World War II. Research was also conducted on public opinion. In World War I, German actions angered Wilson and segments of the American public, persuading Wilson to ask for a declaration of war. While German aggression shaped American opinion in World War II, Japanese action forced the United States to enter the war. In both cases, the tone of aggression that molded the foreign policy of Presidents Wilson and Roosevelt and shaped American public opinion originated from Germany.