“Blood Sacrifice and the Nation: Revisiting Civil Religion” by Carolyn Marvin and David Ingle.
“The Liturgies of Church and State” by William T. Cavanaugh (PDF).
“Messianic Nation: A Christian Theological Critique of American Exceptionalism” by William T. Cavanaugh (PDF).
And my own “Memorial Day and the Religious Syncretism of the State” from a couple years ago.