The Aristotelian sense of piety
We tend to depict piety in a narrow sense. Someone who's "pious" is quiet, devout in church, frequent in prayer, and probably, if we're honest, a bit of a holy roller. In the Aristotelian sense, looking at a virtue solely through its manifestations is a partial picture. The rest can be seen only by understanding its object and, subsequently, the extreme lack or excess of the virtue.
The object of piety (at least in an ancient sense) is love of the gods, or paying them duty. In a Christian context, we would say it is loving God by giving him what we owe him. But we also know that piety can have other manifestations—think of Virgil's "Pious Aeneas." In this respect, the object of piety is devotion to a singular, deserving object of affection, which might be family or, in the modern sense, one's country.
Piety, in an Aristotelian schema, is located on a spectrum between two vices of extreme. On the one end, we'd find something like idolatry. Such a deformation of piety places the experience of loving and paying duty to something above the meaning of being devoted to the object itself, crowding out all other devotions and affections. On the other end, we'd find something like indifference or apathy. Just like the opposite of love is not hate, the absence of zeal in one's affection is the severe form of this virtue. (Think of how many pop songs state scorn and indifference as the torment of the spurned beloved.)
Piety and the American experience
The Fourth of July is our national holiday dedicated to America as an object of our piety. We celebrate the founding of our nation, often commemorating it by recalling the words of our Declaration of Independence and the sacrifices made by our Founding Fathers. Our piety takes a particular shape on this day. We gather together in our communities or families, wear red, white, and blue, eat some traditional fare, and enjoy an evening of exploding, colorful ordinances. (Hey, our piety can be simple, too!)
These ceremonies are so automatic that we can forget they're an expression of real piety. They help make the virtue normal, approachable, so that for a moment it seems to even help erase any unhelpful political, social, and religious divisions.
The expression of piety is so strong among Americans that it's rare to see the deformed extreme of apathy or indifference. Some might argue that low percentages of Americans enlisting in the military or voting shows a lack of pious duty to our country. But between those born here and those who've come to adopt America as their home, the expression of love for this country on Independence Day is nearly universal. That counts for a lot.
As for the other extreme, idolatry, there's more evidence to suggest that affection for paying American homage goes too far. For example, when love of country is mixed up with some other object of devotion producing a bastardization of piety. Think of the portrait of Jesus handing the Constitution to America. Or, more recently, sentiments of nationalism bordering on racial supremacy.
American piety and Catholics
As Catholics in America, we have an important role to play in American piety. Historically, Catholics have been among the most pious Americans, even if we were not always loved by those who came here before us. Remember that Catholicism was outlawed early in many of the colonies, and waves of Catholic immigrants (from Ireland, Italy, and Latin America) were and are treated with suspicion. But, as Catholics, we learn almost instinctively how important piety is.
Our contribution is one of contradiction. Love for country is idiosyncratic. After all, piety toward any object that is impermanent is an imperfect duty. We know that we are made for a higher and more permanent love. Still, we know that devotion to our family, our community, and our country is important because it is an expression of our nature, created to be social, and to live in community with one another. Catholics can confidently lead an expression of the fullness of that love and at the same time, knowing that the object is ever limited, keep from falling into an extreme expression of it, thanks to the constellation of other virtues we constantly strive to cultivate.
This unique situation—even vocation—is evident to non-Americans, too. No less than a German, Catholic pontiff expressed it on our behalf in 2008. Pope Benedict XVI closed his remarks at the White House with the oft-used phrase "God Bless America," but not before he noted and extolled the particular objects of our American piety:
From the dawn of the Republic, America’s quest for freedom has been guided by the conviction that the principles governing political and social life are intimately linked to a moral order based on the dominion of God the Creator. The framers of this nation’s founding documents drew upon this conviction when they proclaimed the “self-evident truth” that all men are created equal and endowed with inalienable rights grounded in the laws of nature and of nature’s God. The course of American history demonstrates the difficulties, the struggles, and the great intellectual and moral resolve which were demanded to shape a society which faithfully embodied these noble principles. In that process, which forged the soul of the nation, religious beliefs were a constant inspiration and driving force, as for example in the struggle against slavery and in the civil rights movement. In our time too, particularly in moments of crisis, Americans continue to find their strength in a commitment to this patrimony of shared ideals and aspirations.