When it comes to Mesomania, the original rationale (reason A) was the belief that Joseph Smith claimed the Book of Mormon took place in Central America. This belief is based on anonymous articles in the 1842 Times and Seasons, long attributed to Joseph Smith.
Because those articles contradict things Joseph actually said and wrote and approved (i.e., Letter VII, Wentworth letter, letter to Emma, Zelph revelation, D&C 28, 30, 32, 128, etc.), Mesomania scholars have sought to link Joseph to the anonymous articles through "stylometry." That effort failed because the scholars refused to share their data, assumptions, and software so their process could be replicated and their conclusions validated or rejected.
As part of reason A, scholars also cited claims made by other early LDS authors, including Benjamin Winchester, Orson Pratt, W.W. Phelps, and, arguably, John Taylor and Wilford Woodruff. Of course, none of these men were involved with the Book of Mormon translation. None visited the records repository in the Hill Cumorah or met with the angels and divine messengers that Oliver and Joseph knew. Nevertheless, the Mesomania scholars accepted these authors while rejecting what Joseph and Oliver said in Letter VII.
Now that Letter VII has become more prominent, they still say Joseph and Oliver were ignorant speculators who misled the Church about the New York Cumorah, but that argument, too, is failing. Once Church members read Letter VII and learn how often it was reprinted and cited, they tend to accept it and reject the two-Cumorahs theory upon which Mesomania scholars and educators rely.
Now that reason A is essentially gone, Mesomania scholars and educators are left only with reason B. I think they realize reason B is illusory, if not complete nonsense, but let's set that aside for a moment.
Reason B is the notion that the text of the Book of Mormon describes the setting with enough precision that it can be mapped, first as an abstract map, and second as a real-world location. That notion is so absurd that it's difficult to believe anyone takes it seriously--the inherent ambiguity of the text is obvious to everyone except these Mesomania scholars and educators who are desperate to find an alternative to Reason A. One would think that the fact there are dozens, or hundreds, of maps based on the text should be proof that the pursuit of an internal map is a fool's errand.
Now we have an "abstract map" being taught at BYU, as if Letter VII never existed and as if the Book of Mormon is a novel like Lord of the Rings that took place in a fictitious, video-game-like territory.
My point here is that Reason B is no more valid than Reason A was. You'll find all kinds of explanations for how the Book of Mormon describes Baja California, or southern Mexico, or Yucatan, or Guatemala, or Panama, or Chile, or any number of places that share one feature in common: the creators of these geographies think Letter VII is false.
We wonder, why the obsession with Meosamerica? I addressed this in my book Mesomania.
The psychology boils down to this. When someone takes a position on an issue that is proven wrong, that person rarely will say, "Okay, I was wrong. The other side that I ridiculed and fought for years was correct."
Instead, that person will shift from the original rationale to something else. When the second rationale proves erroneous, the person will seek a third rationale, etc.
The problem, of course, is that Reasons A and B share the same error: they both reject what Joseph Smith taught. That's why they'll never work, and why they need to be rejected by as many people as possible as quickly as possible.
I ask all LDS scholars, educators, and members to reach a consensus that there is only one Hill Cumorah and it is in New York.