"... but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States."
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof;"
U.S. law is based on English common law, which was based on Roman law. Note that the two concepts in the Constitution that could be called religiously based are the acceptance of slavery and the treatment of women as second class citizens.
The Declaration of Independence mentions Nature's God, not the Christian God. It is also not the basis for the U.S. government, the Constitution is.
The U.S. is no more a Christian nation than it is a white nation.
State Constitutions that Discriminate Against Atheists
Arkansas State Constitution, Article 19 Section 1 ("Miscellaneous Provisions")
No person who denies the being of a God shall hold any office in the civil departments of this State, nor be competent to testify as a witness in any court.
Maryland's Declaration of Rights:
"That as it is the duty of every man to worship God in such manner as he thinks most acceptable to Him, all persons are equally entitled to protection in their religious liberty; wherefore, no person ought by any law to be molested in his person or estate, on account of his religious persuasion, or profession, or for his religious practice, unless, under the color of religion, he shall disturb the good order, peace or safety of the State, or shall infringe the laws of morality, or injure others in their natural, civil or religious rights; nor ought any person to be compelled to frequent, or maintain, or contribute, unless on contract, to maintain, any place of worship, or any ministry; nor shall any person, otherwise competent, be deemed incompetent as a witness, or juror, on account of his religious belief; provided, he believes in the existence of God, and that under His dispensation such person will be held morally accountable for his acts, and be rewarded or punished therefore either in this world or in the world to come."
"That no religious test ought ever to be required as a qualification for any office of profit or trust in this State, other than a declaration of belief in the existence of God;"
Massachusetts' State Constitution, Article 3
"Any every denomination of Christians, demeaning themselves peaceably, and as good subjects of the commonwealth, shall be equally under the protection of the law: and no subordination of any one sect or denomination to another shall ever be established by law."
Comment: Apparently non-Christians are not "equally under the protection of the law".
Note: this part of the Massachusetts' State Constitution was amended. Here is Article XI of the Articles of Amendment:
"Article XI. Instead of the third article of the bill of rights, the following modification and amendment thereof is substituted.
As the public worship of God and instructions in piety, religion and morality, promote the happiness and prosperity of a people and the security of a republican government; -- therefore, the several religious societies of this commonwealth, whether corporate or unincorporate, at any meeting legally warned and holden for that purpose, shall ever have the right to elect their pastors or religious teachers, to contract with them for their support, to raise money for erecting and repairing houses for public worship, for the maintenance of religious instruction, and for the payment of necessary expenses: and all persons belonging to any religious society shall be taken and held to be members, until they shall file with the clerk of such society, a written notice, declaring the dissolution of their membership, and thenceforth shall not be liable for any grant or contract which may be thereafter made, or entered into by such society: -- and all religious sects and denominations, demeaning themselves peaceably, and as good citizens of the commonwealth, shall be equally under the protection of the law; and no subordination of any one sect or denomination to another shall ever be established by law." [See Amendments, Arts. XLVI and XLVIII, The Initiative, section 2, and The Referendum, section 2]."
Mississippi State Constitution. Article 14 ("General Provisions"), Section 265
"No person who denies the existence of a Supreme Being shall hold any office in this state."
North Carolina's State Constitution, Article 6 Section 8
"Disqualifications of office. The following persons shall be disqualified for office: First, any person who shall deny the being of Almighty God."
Pennsylvania's State Constitution, Article 1 Section 4
"No person who acknowledges the being of a God and a future state of rewards and punishments shall, on account of his religious sentiments, be disqualified to hold any office or place of trust or profit under this Commonwealth."
South Carolina's State Constitution, Article VI
"No person who denies the existence of the Supreme Being shall hold any office under this Constitution."
Section 5: The oath of office ends in,
"So help me God."
Tennessee's State Constitution, Article 9 Section 2
"No person who denies the being of God, or a future state of rewards and punishments, shall hold any office in the civil department of this state."
Texas' State Constitution, Article 1 Section 4
"No religious test shall ever be required as a qualification to any office, or public trust, in this State; nor shall any one be excluded from holding office on account of his religious sentiments, provided he acknowledge the existence of a Supreme Being."