Okay well, the typical American breakfast was usually a light meal (e.g. An apple and a bread roll, or leftovers from the night before, etc...) up until the 1920s. In the 1920s there was a bacon selling company called Beech-Nut Packing who hired the father of PR, Edward Bernays to boost their sales. Bernays knew that we as people have greater trust for those we view as authority figures. So he went and asked a doctor a question he already knew the answer to, if a hearty breakfast was better than a small breakfast for your health. When the doctor said yes, he asked if eggs and bacon would be considered a hearty breakfast. The doctor said yes again, and Bernays repeated this process with 5,000 doctors. The media took this as a medical study and ran headlines extolling the virtues of eggs and bacon as breakfast food. Bacon sales soared, Bernays work was done, and the American public adopted eggs and bacon as its breakfast food of choice.

Source: [Video of Bernays himself explaining how he did it.] (https://www.youtube.com/watch?feature=player_embedded&v=KLudEZpMjKU)