Though the First Amendment has established what is commonly referred to as the separation of church & state, the state nevertheless promotes its own brand of civic religion—a religion which is fundamentally incompatible with the Christian faith.
American civic religion features a nationalistic deity: “And the God of public religion is sometimes spoken of as a God bound to the American nation, in Jefferson’s words, “As Israel of old.” While religion has been recognized as playing an essential function with respect to the welfare of the state (serving as the “glue” of society), the Founding Fathers were very careful to avoid defining this religion or its god too specifically. Jon Meacham writes,
“In the public business of the nation, however, it was important to the Founders to speak of God in a way that was unifying, not divisive. “Nature’s God” was the path they chose, and it has served the nation admirably. Despite generations of subsequent efforts to amend the Constitution to include Jesus or to declare that America is a “Christian nation,” no president across three centuries has made an even remotely serious attempt to do so… [Public religion is] a habit of mind and of heart that enables Americans to be at once tolerant and reverent—two virtues of relevance to all, for the Founders’ public religion is consummately democratic. When a president says “God bless America” or when we sing “America! America! God shed his grace on thee,” each American is free to define God in whatever way he chooses.”
Civic religion uses religion to serve its own ends. Since civic religion is designed, in part, to provide a (unified) national identity, in the American context, this requires a vague, pluralistic (and plastic!) god, one who can accommodate the religious sentiments of every citizen.  To put it in theological terms, American civil religion strives to be as ecumenical as possible, encouraging the view that we all really worship the same God, just under different names.
One of greatest dangers of American civil religion is the general belief that this anonymous god is pleased with all good citizens (works righteousness), which can give a false sense of security to non-Christians. Benjamin Franklin stated his own creed in this way, a view he shared with many of the Founders (and a view no doubt held by many today):
“I believe in one God, creator of the universe. That he governs it by his Providence. That he ought to be worshiped. That the most acceptable service we can render to him is doing good to his other children. That the soul of man is immortal, and will be treated with justice in another life respecting its conduct in this. These I take to be the fundamental principles of all sound religion, and I regard them as you do, in whatever sect I meet with them.
While civic religion may have a positive function in society (promoting morality and unity) and even encourages belief in a god, it nevertheless remains idolatrous. Christians should absolutely fulfill their vocations as citizens by praying for their leaders and attending to the concerns of the state, but not in such a way that they confuse the Two Kingdoms (Church and State). A healthy separation between Church and State is necessary to the welfare and proper functioning of both—a fact taught by our Lord (John 18:36; Matthew 22:21) and affirmed by the Founders.
Luther was “quite confident that human rationality could and often would find a good set of positive laws and upright customs to serve a society—no matter how many or few Christians lived in it.” For Luther, any effort at creating a theocratic Christian nation represented a confusion of the two kingdoms, nor did he regard Christianity essential to the proper functioning of the state (as the above quote demonstrates). Since the law of God is written on the heart, we “by nature do what the law requires” (Romans 2:14–15), whether Christian or not. Jefferson agreed: “The virtue of atheists must have had some other foundation [other than religion] than the love of god.”
By contrast to the generic god of American civil religion, the Christian God—that is to say, the One True God, who is not anonymous, but has revealed Himself as Father, Son, and Holy Spirit—is concerned with the welfare of humanity well beyond American borders.
He is a jealous God, intolerant of the worship of false gods. The First Commandment requires exclusive allegiance to the Trinity. He does not want any other gods “before [His] face” (Exodus 20:3). That is to say, God does not want any other gods anywhere in His presence, or in the presence of His children, for that matter. Christians are to flee idolatry (1 Corinthians 10:14; 1 John 5:21), to have nothing to do with false gods, including the idolatrous god of American civil religion.
God warned Solomon to avoid marrying idolaters because they would turn his heart away after other gods (1 Kings 11:2). When the presence of false gods is tolerated, they quickly become familiar and entice the heart to worship. This was certainly the case for Solomon (1 Kings 11:3–4), and it remains a danger today as well.
This means that Christians cannot stand side by side with Jews and Muslims in addressing the anonymous god of American civil religion. We should avoid giving a false witness to God’s identity by singing to this nationalistic, generic deity (e.g., “God Bless America”). Ceremonial deism such as we find in the Pledge of Allegiance is, at best, meaningless. For those who believe in different gods to come together and participate in polydox prayer vigils is an act of syncretism (and therefore a violation of the First Commandment). Anything that deliberately suppresses the truth about God (as is the case in American civil religion) or treats Him as one god among many should be avoided. As David Adams writes,
“As Americans we may (and do) have to tolerate the worship of other gods within civil society, but as Christians we violate the First Commandment any time we tolerate or encourage the worship of other gods in the presence of Yahweh. The only possible conclusion upon reading the Word of God is that the people of God must not be a party to any activity that encourages or promotes the worship of other gods.”
 Meacham, American Gospel, 22
 In the minds of the Founders, the need for religion or belief in a god was considered essential for the good of society.
 The Declaration of Independence refers to the American deity in four ways: “Creator”, “Nature’s God”, “the supreme judge of the world,” and “divine providence.” There is no mention of any deity in the Constitution.
 American Gospel, 23.
 Since monotheism has predominated in the American religious consciousness, rather than add multiple gods to the American pantheon, it is common to speak of one ‘god’ in very vague, lowest common denominator terms.
 Isaacson, ed. A Benjamin Franklin Reader, 376–378.
 A fact which is also borne out in history. The papacy is a prime example of what happens when the Church meddles in the affairs of the state. See also Article XXVIII of the Augsburg Confession and its Apology (Of Ecclesiastical Power).
 Kolb, “Christian Civic Responsibility in an Age of Judgment,” Concordia Journal 19 no. 1 (January 1993): 20.
 This is not to deny the importance of evangelism. Those who participate in American civil religion often do so under the guise of evangelism, when in fact participating in civic religion couldn’t be any more unevangelical as it compromises the Christian witness. Mere engagement with the world is neither evangelical (“mission” work that is limited to doing acts of mercy; showing up at a civic event; so-called “ministry” of presence) nor an end in itself with respect to the mission of the Church.
 American Gospel, 29.
 As a fundamental expression of (idolatrous) American civil religion, the phrase (and song) “God bless America” is best avoided by Christians. The attempt to co-opt such an essential expression from another religion would be akin to borrowing the term “Allah” for God in an effort to “baptize” it for Christian use. Such language is so intricately tied to idolatry as to make it beyond use for Christian purposes.
 The Anonymous God, 238.