The Catholic Church in America in the 19th century would have never featured an American flag anywhere in sight. This trend began in World War I: the German parishes were pressured to show their loyalty to the state and its war. The trend picked up steam in World War II, when the Italians too were suspected and so had to declare their loyalty. The flag issue became universal during the Cold War when everyone was expected to rally around the nation in its fight against its foreign adversaries.
But looking in back in time to the 18th and 19th century, to say nothing of the European middle ages and back before the invention of the very idea of the nation state, this entire project would have been completely unknown: the Church nowhere swears allegiance to the state and Catholic Christians are citizens first of a universal kingdom with a ruler chosen from all eternity. Our vows are made unto the Lord.
In recent times, very recent times, the Catholic Church in the U.S. has been singled out for special pressure from courts and judges, and this is changed many aspects of parish management in ways that truly do represent an intrusion of politics and state issues in a sacred space. This is a tragedy that is gravely regrettable, even deeply threatening, and one that should not go unnoticed. We are being pressured yet again.
However, the Church, as Benedict XVI has written, does not derive its legitimacy or rights from secular or civil sources; its existence transcends time and place and its legitimacy is internally confirmed. Its liturgy should and must represent an exit from temporality and political issues and enter touch elements of eternity: this is where all its art and furnishings and music must point.
Hence, there is a sense in which the worship space must be a sanctuary from the grittiness and cruelties and manipulations of such issues as nationalism and profane forms of earthly patriotism. Signs and symbols drawn from world profane politics constitute a distraction from this essential task at hand.
It is for this reason, and for the reason that nationalism is not part of our tradition, that conventional songs of secular-style patriotism cannot contribute to the liturgy but rather depart, even radically, from its spirit and intent. We live in times of hyper-nationalism, war, and all-intrusive statism that the Church is called to resist in favor of truth, beauty, and true salvation. It is an easy-enough step to sing the propers of the Mass and leave the marches and statements of national fidelity to civic-pride parades.