Curious Armen, I am sitting here with a copy of the constitution in my lap... I don't see anything prohibiting religion from government. In Article 3 it covers the freedom of religion, speech, press, and assembly. The part regarding religion,

"Article of the third.... Congress shall make no law respecting an establishment of religeon, or prohibiting the free exercise thereof"

Hmmmm.. don't see anything there about the absense of it, only that the government will not establish a religion.