If atheists in the USA are getting angry (and vocal about their anger), maybe they have good reason to.

No, I don't know that atheists should be considered as citizens, nor should they be considered patriots. This is one nation under God.

George Bush, Sr. (then Vice-President), August 27, 1987

The following statements are taken from the actual constitutions and laws of American states. The source for the list is at goodlessgeeks, which also provides links to the relevant documents so people can see this legalised bigotry for themselves.

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.

Arkansas State Constitution, Article 19 Section 1 (“Miscellaneous Provisions”)

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.

Maryland's Declaration of Rights, Article 36

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.

Massachusetts' State Constitution, Article 3

So.. anyone that's not a Christian isn't “equally under the protection of the law”.

No person who denies the existence of a Supreme Being shall hold any office in this state.

Mississippi State Constitution. Article 14 (“General Provisions”), Section 265

Disqualifications of office. The following persons shall be disqualified for office: First, any person who shall deny the being of Almighty God.

North Carolina's State Constitution, Article 6 Section 8

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.

Pennsylvania's State Constitution, Article 1 Section 4

No person shall be eligible to the office of Governor who denies the existence of the Supreme Being; …

South Carolina's State Constitution, Article 4 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.

Tennessee's State Constitution, Article 9 Section 2

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.

Texas' State Constitution, Article 1 Section 4