The term "fundamentalism" has its roots in specific forms of American Protestantism that arose around the turn of the twentieth century in reaction to liberalizing and modernizing trends within the church. In this book, Mark Massa argues that an analogously reactive, militant, and sectarian "fundamentalist" movement emerged within American Catholicism in the decades after World War II, for a similarly complex mix of theological and cultural reasons. In Catholic Fundamentalism in America Massa gives the first account of the Catholic form of the anti-modernist impulse.

Massa recounts how Catholic fundamentalism has reacted both to the teachings of the Second Vatican Council and to the tensions of America's pluralist, secular culture. Like their Protestant cousins, Catholic fundamentalists combine a sectarian understanding of religion with an aggressive anti-progressive stance. Their main enemies were not Protestants or secular Americans, but other Catholics who didn't share their extreme views. Also like the Protestant fundamentalists, Catholic devotees of the fundamentalist impulse have sought (and found) political conservatives with whom to make common cause on a range of issues, such as the place of women in American culture, the value of pluralism within the Church and the larger culture, and the importance of cooperation with non-Catholics. Contemporary Catholic conservatives merge theological and political impulses into movements that "punch above their weight" within the community through their clever use of social media.

Through seven portraits of individuals and movements that embody the Catholic fundamentalist impulse, Massa demonstrates how the Catholic Right, like its evangelical Protestant counterpart, has reacted to--and fought against--modern American culture.