The major trends that transformed American society in the 1920s were the increased availability of consumer goods and of options for entertainment. These trends changed American society, making it a society that was more centered around leisure than it had been before.
By the 1920s, many kinds of consumer goods were becoming more and more available. This was partly because of changes in manufacturing technology. The greatest example of this was the Model T, which became affordable to many Americans because of advances in assembly line technology.
At the same time, entertainment options were becoming available. There were radios and there were movies (in addition to cars) that were offering people things to do with the spare time that had been freed up by labor saving devices that were becoming avaialble to middle class Americans.
With Americans having more time, more consumer goods, and more entertainment choices, the American society became the society of the Jazz Age, centered around leisure and fun much more than it ever had been.