In the 20th century the United States became the foremost  international power,  measured by wealth, military might, and cultural influence. In material terms the American nation seemed the epitome of success.

But this century also brought contradictions and tensions.  The population became even more diverse, its population growing rapidly after World War II with many immigrants from non-European continents bringing religions distinct from the Judeo-Christian traditions that had become part of American life by the first quarter of the century. These new American communities brought new challenges for defining American identity.  During the last decades of the century the relation between the Many and the One in American life became an increasing source of controversy, with contending visions for the religious meaning of the American nation.

During the last half of the century changes within American Protestantism were another source of diversity and conflict.  The long established  mainline denominations (Presbyterians, Methodists, Baptists, Congregationalists, Episcopalians, Lutherans) faced ever greater competition from new churches spawned by Evangelical and Pentecostal movements. And  many of the mainline churches were also weakened by conflicts between conservative and liberal factions over issues of gender, biblical authority, and social and political questions.

This period, roughly the last three-quarters of the 20th century, can be plotted into three periods:

1920s to the 1940s: Twilight of Protestantism? Religious "Depression" and Controversies

1940s to  the 1960s: Religious Revival for a Super Power

1960s to Present: Tensions and Culture Wars in Post-Christian America