Automobiles have had a huge impact on the national development of the United States. Let us look at two ways in which this has happened.
First, the process of making and maintaining automobiles has caused a great deal of economic activity. Auto manufacturers became a major part of industrial America in the 1920s and beyond. They supported many other businesses that made parts for the cars. The industry also supported a huge network of gas stations and other support facilities.
Second, the growing number of automobiles was a boon for other industries that were not related. This was because of the development of trucking as a means of transport. As trucks became more common (as did roads for them to drive on), America's economy became more and more interconnected. This allowed for an expansion of the American economy because it created a huge transportation web that connected every part of America to every other part.
In these two ways, the automobile was a form of technology that had a huge impact on the economic development of the US.