More women in the work force, high divorce rate, and postponing marriage are three main factors that account for changes in the American family.
In the 1960's during the "feminist era", women began coming to the workforce to be equal to men and to help support the family. In today's economy, it's become pertinent in most middle class and lower class families that both partners work just to be able to make ends meet.
The high divorce rate in America has seen a steady increase up until recently; which has been going down but ever-so-slightly.
Postponing marriage is due to the Millennial generation wanting to prevent a higher divorce rate.