Describe the major changes that took place in the practice of religion in America in the early nineteenth century and the impact these had on American society.

The period encompassed in this question witnessed the emergence of what historians call the Second Great Awakening, a major transformation in American Christianity. These major changes that occurred in the practice of religion can best be described as its "democratization." This was true both in form and in practice. Many of the preachers who conducted the revivals of the Second Great Awakening preached in an emotional, accessible style free from the formality and stuffiness that characterized some church services. This attracted many Americans in a period known for advancing political participation and democracy, particularly for white males. Evangelical Christians also emphasized the individuality of people and their ability to form a direct relationship with the divine. An individual's salvation was dependent on their willingness to accept God, not any other, external factors, and it was certainly not limited to a small group of "elect," as the Puritans had taught. So religion was in every way more accessible to ordinary Americans.
As for how these changes affected American society, the short answer is that they served as a motivating factor for the many reform movements that emerged during the period. The new evangelism emphasized the ability of people to change their own lives, and even the world. For many, this found an outlet in efforts to reform the many social ills—slavery, Indian removal, alcohol abuse, asylums, and countless others—that plagued American society in the period. In a less tangible way, this new way of thinking about faith gave meaning to ordinary people whose lives were increasingly affected by impersonal market forces during the Market Revolution. It was no coincidence that these evangelical movements first emerged in communities, like those in the "burned-out" district of New York, that had most felt the effects of these economic and social changes.
http://nationalhumanitiescenter.org/tserve/nineteen/nkeyinfo/nevanrev.htm

https://www.ushistory.org/us/22c.asp

Religion in America became more diverse.  Groups such as the Latter-Day Saints (Mormons) formed their own churches.  The United States had more Catholics as Irish immigration increased.  While these denominations were not accepted in mainstream Protestant America, they were quickly becoming a presence and drew increasing number of followers.  
The Protestant Church grew as well, with increasing numbers of Presbyterians, Baptists, and Methodists.  The Second Great Awakening, which began in the 1820s, brought more people into church membership.  One of the first things that frontier communities did was form a church.  Churches also spoke out more against social issues such as slavery and alcohol.  The African Methodist Episcopal Church started during this period though its numbers would not skyrocket until after the Civil War.  Many churches even split over doctrine differences, creating new denominations such as Southern Baptists and Missionary Baptists.