The relevant portion of the 1st Amendment states simply:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof
Lets break that down. It starts with 'Congress'. This refers specifically to the US Congress. It doesn't say government, it means Congress, the legislative body.
Now, compare that very simple text of the 1st Amendment to the text of my state's Constitution as it pertains to religion.
"Section 16. Free exercise of religion; no establishment of religion.
That religion or the duty which we owe to our Creator, and the manner of discharging it, can be directed only by reason and conviction, not by force or violence; and, therefore, all men are equally entitled to the free exercise of religion, according to the dictates of conscience; and that it is the mutual duty of all to practice Christian forbearance, love, and charity towards each other. No man shall be compelled to frequent or support any religious worship, place, or ministry whatsoever, nor shall be enforced, restrained, molested, or burthened in his body or goods, nor shall otherwise suffer on account of his religious opinions or belief; but all men shall be free to profess and by argument to maintain their opinions in matters of religion, and the same shall in nowise diminish, enlarge, or affect their civil capacities. And the General Assembly shall not prescribe any religious test whatever, or confer any peculiar privileges or advantages on any sect or denomination, or pass any law requiring or authorizing any religious society, or the people of any district within this Commonwealth, to levy on themselves or others, any tax for the erection or repair of any house of public worship, or for the support of any church or ministry; but it shall be left free to every person to select his religious instructor, and to make for his support such private contract as he shall please."
Very much more detail. It even specifically mentions a creator and Christianity in the text. The language is very careful not to establish Christianity as the state religion though. However, I see nothing in the text that would prohibit the display of the ten commandments on a court building, or a cross in a state park honoring veterans. In fact I consider the prohibition of the display a violation of the free exercise thereof. Then again, it is never Congress that prohibits this, it's always a judge. In my opinion a judge's role is to uphold the law as written, not 'interpret' the law as they see fit which is what we've all been taught to accept.
I know that many judicial precedents can be cited that changes this interpretation. It is my opinion that these precedents are "bad law" and further illustrates my concern over the judiciary subverting the law rather than upholding it.