I have heard all my life that when the constitution of the United States hangs by a thread, that it will be saved by the Priesthood. Can you tell me if there is anywhere that this is written or is it just one of those tells that gets passed around.
The statement that you refer to was a written statement by others who heard it and passed it around. The statement was reportedly made by Joseph Smith, but it was not recorded by him, but by others who heard him make the statement. Joseph Fielding Smith in Doctrines of Salvation, p.326, recorded the following—
“The statement has been made that the Prophet said the time would come when this Constitution would hang as by a thread, and this is true. There has been some confusion, however, as to just what he said following this. I think that Elder Orson Hyde has given us a correct interpretation wherein he says that the Prophet said the Constitution would be in danger.
“Said Orson Hyde: ‘I believe he said something like this-that the time would come when the Constitution and the country would be in danger of an overthrow; and said he: ‘If the Constitution be saved at all, it will be by the elders of this Church.’ I believe this is about the language, as nearly as I can recollect it.’”
Ehat and Cook report the following—
“The History of the Church account is an amalgamation of the reports in the Joseph Smith Diary and the Nauvoo Neighbor. The report by Levi Richards is here published for the first time. A reminiscent account of this discourse by James Burgess contains the essential details found in the other three accounts published here, and adds that the “Constitution and Government would hang by a brittle thread.” (Joseph Smith, The Words of Joseph Smith: The Contemporary Accounts of the Nauvoo Discourses of the Prophet Joseph, compiled and edited by Andrew F. Ehat and Lyndon W. Cook, p.279)