The large scale change referred to here is the Market Revolution. This revolution led to a US society that was less communal and more individualistic. Before the changes, Americans lived together in small communities where people took care of one another. But now, they lived more in larger communities where they did not have familiar neighbors to be of help in times of trouble.
These large scale changes helped lead to religious revivals. This was the Second Great Awakening that swept through the US in the early 1800s. This religious revival inspired people to think that society could be perfected and that they had the responsibility to try perfect it.
From these two influences came the reform movements. There were new problems caused by the growth of society and the loss of community. There was also the attitude that people should try to fix those problems. When combined, these led to the antebellum reforms.