Joe Carter and John Coleman are two traditionalist Christian thinkers who well understand the issue of civil religion and the Pledge of Allegiance and they've written excellent articles on the matter. See Carter's and Coleman's (which cites Carter's). Whatever the merits of Michael Newdow's legal case, and whatever the policy merits of keeping God in or taking God out, it's important to understand what "under God" means. And it's not under the Christian God or even under the "Judeo-Christian" God, but rather under the God of the American Civil religion, which is under the God of Jefferson, J. Adams and Franklin (who thought Hindus and Muslims worshipped the same God Jews and Christians do). And they in turn whether they consciously knew it (arguably they didn't) followed Rousseau's plan.
Carter notes something profoundly important. There probably ARE many Christians who DO think it's under their God. And they are either ignorant or fooled. This same dynamic existed during the Founding era when the first four Presidents spoke to a Christian populace speaking as though they worshipped the same God. And then spoke to Native Americans...and acted as though they worshipped the same God (the "Great Spirit"). Carter writes:
America has done a fine job of incorporating Rousseau's "dogmas of civil religion", keeping them "few, simple, and exactly worded." We have restricted such sentiments to the most unobtrusive areas, allowing "In God We Trust' to be printed on our coins and the phrase "under God" to slip in our Pledge of Allegiance (which, curiously, isn't a pledge of "allegiance" to God but to a flag). We allow recognition for a "Divinity, possessed of foresight and providence" but what we don't allow is the recognition of the Christian God. And that is what should give Christians pause.
There is a vast and unbridgeable chasm between America's civil religion and Christianity. If we claim that "under God" refers only to the Christian conception of God we are either being unduly intolerant or, more likely, simply kidding ourselves. Do we truly think that the Hindu, Wiccan, or Buddhist is claiming to be under the same deity as we are? We can't claim, as Paul did on Mars Hill, that the "unknown god" they are worshiping is the God of Abraham, Isaac, and Jacob. The Pledge is, after all, a secular document and the "under god" is referring to the Divinity of our country's civil religion. Just as the pagan religion of the Roman Empire was able to incorporate other gods and give them familiar names, the civil religion provides an umbrella for all beliefs to submit under one nondescript, fill-in-the-blank term.
Coleman recognizes that "under God" is a quasi-secular, not an authentically biblical idea. But the irony is the quasi-secular thinkers of the Founding era (America's key Founders) were the ones who gave us this generic civil religion because they thought "under" a generic "God" was a glue that could hold society together. Now the secularists like Newdow are on the other side. As he writes:
That is why, for generations, the Michael Newdows of this world recognized that acknowledging a generic higher power was helpful, not harmful to the citizenry. It held the nation together. It calmed the populace. It united us under a creed. To the irreligious (like many of our Founders) hollow recitations of Under God would seem paltry penance for the benefits afforded by state religion's civil unity.
To the devout, however, "under God" may pose a more serious moral threat. One of the most basic tenets of both Judaism and Christianity is Yahweh's statement in the Ten Commandments, "Thou shalt have no other Gods before me;" yet every day millions of Christians, Muslims, and Jews stand first, not to pray to the God of Mohammed or of the Cross, but to pledge allegiance to the god of city, state, and country.
Both articles demand serious thinking. Make sure you check them out.