The First Amendment to the U.S. Constitution clearly lays out prohibitions for the American government to promote or infringe on religion. It specifically uses the indefinite article "an" and not the definite article "the," which might otherwise be construed to apply only to a national or state-sponsored religion. The article "an" essentially means "any." The so-called religious establishment clause begins the amendment, which also speaks to the freedom of speech and the press. The implications of the amendment are unequivocal, not hard to understand.
“Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances."
