I agree, the USA is a secular nation, albeit built on Judeo-Christian principles. There should be freedom of, and respect for, all religions and those persons abstaining.<quoted text>
Nor would I want a government that would deny anyone their right to believe or not believe as their conscience dictates. However the problem is that history has shown that religious liberty is denied when one particular religion is allowed to "infect" government. Neither government "infecting" religion nor religion "infecting" is a good thing; hence Jefferson's "wall of separation" between church and state.
"Because religious belief, or non-belief, is such an important part of every persons life, freedom of religion affects every individual. Religious institutions that use government power in support of themselves and force their views on persons of other faiths, or of no faith, undermine all our civil rights." -- Thomas Jefferson, to the Virginia Baptists (1808)
You did give me a chuckle with your comment;
"However the problem is that history has shown that religious liberty is denied when one particular religion is allowed to "infect" government."
Surely you must be aware that currently over 50% of the Executive, Legislative and Judicial Branches of the Federal Government is controlled by Catholics.
With the remaining balance being nearly all Protestant and Jewish persons.
But the Separation of Church and State clause is sound and since no-one can possibly speak with more authority on this subject than George Washington himself, here is what he said in the Farewell Address to the Congress and to the people of America; and his guidance deserves to be put in front of all the others' opinions:
"Of all the dispositions and habits which lead to political prosperity, Religion and morality are indispensable supports.
In vain would that man claim the tribute of Patriotism, who should labour to subvert these great Pillars of human happiness, these firmest props of the duties of Men & citizens.
The mere Politician, equally with the pious man ought to respect & to cherish them. A volume could not trace all their connections with private & public felicity.
Let it simply be asked where is the security for property, for reputation, for life, if the sense of religious obligation desert the Oaths, which are the instruments of investigation in Courts of Justice?
And let us with caution indulge the supposition, that morality can be maintained without religion.
Whatever may be conceded to the influence of refined education on minds of peculiar structure--reason & experience both forbid us to expect that National morality can prevail in exclusion of religious principle.
'Tis substantially true, that virtue or morality is a necessary spring of popular government.
The rule indeed extends with more or less force to every species of Free Government. Who that is a sincere friend to it, can look with indifference upon attempts to shake the foundation of the fabric.