Jay, I don’t see American history helping you much on your bootstrapping argument about past practice and the National Day of Prayer.
Remember that Thomas Jefferson actually vetoed day of prayer resolutions as President-and those were usually focused on some special event. I can find no record at all of any effort to set aside one specific day every year as a countrywide time for religious ritual. Can you?
Moreover, even though we all know that some states had “official religions” at the time the First Amendment was ratified, there is no doubt that the same “federalist” principle that lead some to question the wisdom of a national army would lead to reticence about a national day for religiosity.