If Mr. Coons had had additional time to respond, perhaps he would have mentioned this case:
The case involved a school district that was reimbursing costs associated with school buses for public and private schools, including private religious schools. While the justices disagreed whether this was sufficiently distinct from the religious function of the school to not constitute support of religion (the majority thought it was all right), they all agreed that the establishment clause constituted a "wall of separation of church and state" -- for school districts, for states, and, obviously, for the federal government. The quote is from TJ, in a letter to the Danbury Baptists of 1802:
If Ms. O'Donnell wanted to make the case that a state _could_ establish a religion, she need look no further than Massachusetts which, as a colony, had near complete identity of church and state, and which did not finish disentangling them until sometime in the 19th century, well after the ratification of the Constitution with its Bill of Rights.
I don't have a reference for this piece of speculation, but I suspect that the details of the Everson case contained the seeds of what the Bush Administration would create in the name of "faith based initiatives". Given the strong negative reaction to those initiatives from a substantial proportion of the population, I don't think Ms. O'Donnell can feel too optimistic even in this limited idea of state support for religious efforts -- much less something even the Black court was unwilling to contemplate in 1947.
The takeaway for anyone confronted with someone from the right wing echo chamber in which Ms. O'Donnell can apparently be found is simple:
The first amendment
Everson v. the Board of Education
And a lot of other cases before the Supreme Court.
Which is to say, if you think you can find support for the Trinity in the Bible, you can _definitely_ find support for the separation of Church and State in the Constitution. Me, I think the textual support for the separation of Church and State is stronger in the Constitution than the support for the Trinity is in the Bible -- but I was raised a JW. Given that Ms. O'Donnell thinks you can find a ban on masturbation in this text:
she certainly should not have trouble understanding the line of reasoning which finds a wall of separation in the Establishment clause.
Keep reading -- then take a look around and see if you can find any fundamentalist Christians walking around minus a body part or so. I don't think even most fundamentalists take that particular part of that particular sermon that particularly literally.