"The theme of Gatsby is the withering of the American dream"

When you look back to America's earliest history you see the idea of the stereo typical "American dream". This original idea is that America is a place for freedom and where the hard working are rewarded not based on their family history or who they know, but the effort they put forth.
For some, this is still the drive to many thousands of immigrants that come to our country every year. The idea that across a border you can get a job serving food and then have money to send home, or to provide for your new homer is the reason for our immigration overpopulation. And when you think of it that way, it's almost encouraging that some still view America as a great prosperous country.
The Great Gatsby challenged that idea that was continuously falling since beginning of the industrial age. Gatsby started off in the war, a common American dream, fighting for your country. Then he met Daisy, the only love of his life. Then he shifted to his next dream to Daisy. The two fell in love and nothing could hold them back except for the insufficient funds on Gatsby's part. Gatsby had to leave for the war and came back to find his love with a wealthy man. This twisted his dream for the last time, he now shifted his focus to the dream of money which ultimately meant winning Daisy.
This conflict of changing interests is the message of the true theme of The Great Gatsby. Americans have changed their dreams from life, liberty and the pursuit of happiness to money, credit, and the pursuit of wealthiness.