I believe that in this practice it is, but that's just my belief. Aside from constitutionality, it's just not conducive to the peace of the nation to go recognizing one religion or religious sect above all others in such a blatant manner.
Look at our anti-Catholic Protestant friend on this list. I believe that if the government officially recognized Catholicism as the preferred Christian sect (especially since he doesn't even believe they are Christian), he would be offended and very mad at the government. I'm sure he would consider it a direct governmental interference in religion and be fighting against it.
Apologies to Gargantua, of course, if I am incorrect. You are entitled to your beliefs.
Are you going to recognize the Church of Satan and the Scientologists and others of similar ilk?