"As the Government of the United States of America is not, in any sense, founded on the Christian religion..." This quote is taken from the Treaty of Tripoli "Article 11". This Treaty was submitted to the Senate by then President John Adams in 1797, click below LINK:
The Treaty is clear...the GOVERNMENT of the United States of America IS NOT, IN ANY SENSE FOUNDED ON THE CHRISTIAN RELIGION! What does that mean? It means although the United States of America is predominantly a Christian Nation the Government isn't! The NATION and the GOVERNMENT are two different entities which is why the Untied States of America's Constitution supports freedom of religion (U.S. Constitution Amendment 1).
According to the Constitution (NOT) the Bible, gays have the legal right to marry! Why? It's simple yet complicated. The Government can't prohibit gays from marrying simply because religious books speaks thwarts homosexuality. The Government of the United States of America is ran by the Constitution, not the Bible.
This is why in many States gays are winning the legal right to marry. The Government can not discriminate based on religious belief, sex, color, or creed. Then, there's the SEPARATION of Church and State that must be taken into account as well. Click below LINK:
In my humble opinion the Church has no legal right to tell the State what it should or shouldn't do, just as the State has no moral right to tell the Church what it should or shouldn't accept! Should gays have the legal rights to marry all across the United States of America? Of course they should!