Elizabeth Stoker Bruenig in TNR:
There are, of course, a slew of issues with establishing any state faith, chief among them the First Amendment. Naming state religion would also contravene all Republicans supposedly hold dear when it comes to maintaining a small unobtrusive government. But aside from the illegality and irrationality of it, naming Christianity the United States’ national faith would do damage to the faith and faithful even if it did somehow shore up national morality. This is because national faiths, for better or worse, tend to morph into nationalism with a faith element, rather than a faith that happens to be practiced by a particular nation.
This is already true of right wing rhetoric wherein Christianity is made to stand in for American conflicts or situations. Earlier this month, for example, President Barack Obama faced censorious outcry after noting that Christians of the past carried out the Crusades; with Republicans like Governor Bobby Jindal accusing the president of going hard on Christianity in lieu of ISIS, it’s clear the Crusades were, in this instance, turned into an analogy of a purely modern conflict, with Obama implied to be on the wrong side. By criticizing Christianity instead of Islam he was understood to take the side of foreigners rather than Americans.
With Christianity serving so often as a cheap byword for Americanism, it’s no surprise that 54 percent of Republicans believe the president is an undercover Muslim, and that a handful of their vocal politicians believe he does not love America. These are twin suspicions, both impossible to prove, both based on speculation about the president’s internal states, which trade evidence among them, such as the fact that Obama will not say that America is at war with Islam.
Were Christianity named our national religion, it would only be dubbed such to serve a particular national purpose, that is, to straighten out our morals or boost morale for our confrontation of terrorism abroad. But to do this would be to force Christianity into the servitude of particular national interests, which would only further the degree to which the Christian faith is already wrongly conflated with specific American political aims.
More here.