The American Dream is and always has been a myth. The US between 1776 and 1936 was a difficult place in which to live. Most people died poor and broke. The "American Dream" of consumerism and easy living that we understand today in the US did not develop until the 1940s and early 1950s with residential television sets and commercial broadcasting. It was consumerism mixed with the after-effect of the progressive New Deal reforms that FDR had started in the 1930s. Today, those reforms are all but gone and people are back to working until they die as old men and women.
I think the original "American Dream" was one of opportunity for those who were willing to go the extra mile and take it. In the 1510s, Hernan Cortes was a glorified civil service clerk in Spanish Cuba who raised a small army and conquered the Aztec Empire of Central Mexico. After that, he was made a Duke of the region by King Charles and became a rich, powerful, and famous man. Andrew Jackson was a smallpox survivor and poor orphan from the North Carolina frontier who argued his way into becoming a successful lawyer in Tennessee; then a politician, businessman, and conqueror of Florida. Eventually, he became President of the US. In the late 1700s, John Jacob Astor traveled to Puget Sound and established a valuable fur-trading business that made his family the richest and most powerful in New York. Joe Kennedy got into bootlegging alcohol during the 1920s prohibition and made his family very wealthy and powerful. The traditional opportunities in the Americas seemed to be in becoming rich or conquering lands--on varying scales. Today, fame has crept in to join these traditional "dreams". Becoming a singer, actor, athlete, or highly-paid artist or media personality is what many young people dream of. But I still think the old original dreams of wealth or conquest are still there and are still strong in some people's heads.