There are many factors in the history of suburbia in the United States, which, before World War II, was a largely rural country and still trying to come out of the Great Depression. During World War II, there was no production of cars at all, because all manufacturing resources went toward the war effort, and very little construction of housing. However, there were jobs now, particularly war-related production, and World War II marked the end of the Great Depression.
Once the war was over, there was a pent-up demand for cars, which began production again, a pent-up demand for housing, and a baby boom, resulting from all those soldiers returning home. Many GI's took advantage of the educational opportunities available under the GI Bill, and most had no difficulty finding work. The federal government made it easier for GI's to get mortgages, with little money down and reasonable monthly payments.
All of these factors resulted in an incredible expansion in the areas between the cities and the countryside, where land was cheaper and cars enabled people to reach it. People who were beginning to have children again wanted more space for their growing families, and builders and auto manufacturers were able to provide what they wanted.
I am a baby boomer myself, and I remember my parents telling me that when my dad came home from the war, all they could find was a one-room apartment at first, because of the housing shortage.
In the US Levittowns were the beginnings of suburban growth. After World War II with the sudden increase of men coming home after the war started a serious housing shortage. The GI bill of 1944 provided money to educate and build houses for the returning soldiers. A man named William Levitt bought thousands of acres of land outside of cities like New York and Philadelphia Levitt then proceeded to plan out the construction of towns full of prefabricated houses. (Center for Lifelong Learning and Development)