As always, I'm not speaking for anyone else. I'm only relating my own thoughts. Believe whatever you want. It's fine with me. If the citation cartel had simply given a fair hearing to the "Heartland" in the first place (let alone Oliver Cowdery), I may not have started this blog.
I've been reading material published by the citation cartel for decades. The connection between Mesoamerica and the Book of Mormon boils down to 1) "correspondences," 2) additions to the text (e.g., headwaters of Sidon, narrow strip of mountainous wilderness), and 3) claims the text is translated incorrectly (horse should be tapir, etc.). The idea of correspondences boils down to this: 1) The Nephites farmed; 2) the Mayan farmed; 3) therefore, the Nephites were Mayans. I've addressed many of these so-called correspondences specifically in this blog already, so I won't rehash those.
For BMAF, such "correspondences" constitute evidence. Members of the club necessarily "see" Mesoamerica in the Book of Mormon or they wouldn't be members of the club. To me, they constitute examples of human culture that are shared around the world and throughout time.
Now I freely admit that Heartlanders (to use the BMAF term) could be equally guilty of wearing Heartlander lenses. People who promote Baja, Panama, Chile, Cambodia or any other location can also wear lenses customized for their respective preferences. But there's a huge difference. BMAF and Mesoamerica have been the scholarly consensus for decades. Their monolithic approach has filled lds.org media, lesson manuals, and CES instruction. It is imprinted on the minds of LDS from Primary age forward. Few if any LDS have not already had the Mesoamerican lenses placed on their heads. By definition, anyone who disagrees has entertained at least more than one viewpoint (Mesoamerica plus the one they prefer). By contrast, you never need to seriously consider an alternative viewpoint to stick with the default Mesoamerican idea. That's why BMAF has been considered credible all these years despite their mission statement.
Next I'll look at 4 different types or categories of evidence.
1. The text itself. Most people writing on this topic probably place the text as the "most important" evidence. (I agree in a sense, but it's not a useful point because evidence is a seamless web, not a hierarchy; i.e., truth becomes apparent through all types of evidence, and they interact and must be considered together). Usually when someone says the text is the "most important," they mean their interpretation of the text is the most important. The problem with the text, of course, is that interpretation is subjective. An obvious example is the way BMAF conflates the terms narrow neck, narrow neck of land, and small neck. I think they are different terms because they refer to different things. To me, this is obvious; to others, their point of view is obvious. Without the author (Mormon) available, we have to make a decision about interpretation and go with it. The subjective nature of interpretation creates the problem with abstract maps; no two people can possibly come up with identical, or even similar, abstract maps because the text is so vague. Some people think that if enough people, working together, develop a "consensus" interpretation, then that should lead to a "consensus" map, but the logical fallacy of that approach is self-evident.
2. The other scriptures. The D&C and PofGP provide relevant information; some accept it, some don't, and some apply various interpretations. For example, when Joseph referred to Cumorah in D&C 128, it was in the context of universal acceptance of Letter VII's explanation of Cumorah (which was in Joseph's own journal). Yet I've read claims that Joseph was referring to an unknown hill in Mesoamerica, Others claim Joseph was merely repeating a tradition started by unknown persons at unknown times. Some people accept as literal revelation D&C 28, 30, and 32, which identify the Lamanites as the Indians living in New York, Ohio, and Missouri. Others think these sections reflect merely an "early belief" shared by the early Saints. (This seems to be the position taken by the Joseph Smith papers and the Church History museum, as I've discussed).
3. Church history. For some people, the Frederick G. Williams note about Chile is the most important evidence. For others, the 1842 Times and Seasons are the most important. For others, Letter VII is the most important. Still others think Joseph was merely speculating, which logically could put the Book of Mormon anywhere in the world. (The text itself does not even state what continent the people landed on, what ocean they crossed, etc.)
Readers here know that I 1) reject the Williams note, 2) think Winchester wrote the anonymous Times and Seasons articles, and 3) accept Letter VII. Regarding Letter VII, I think Joseph and Oliver knew the final battles took place in New York. The BMAF objection that they never claimed revelation about that is a red herring; i.e., it doesn't matter, because they visited the room where Mormon stored all the plates (wagon loads full) and it was in the New York Cumorah. Any reading of the text places Mormon's Cumorah at the scene of the last battles. BMAF skirts this by claiming Joseph and Oliver never visited an actual site; it was merely a vision. IOW, they shared a vision of visiting a site in the hill Cumorah three times (at least), and they described the room and its contents in detail (including changes from one visit to the next), but the vision forgot to reveal they were actually "seeing" a site somewhere in Mesoamerica. (I have a chapter on this in the Second Edition of Letter VII, to be released soon. There is a lot that has never been discussed about this, and I lay it all out in this chapter.)
4. Extrinsic evidence. Anthropology, geology, anthropology, geography, and other sciences can help us make sense of the text. I've addressed these many times on this blog. One example is volcanoes. BMAF insists the Book of Mormon describes volcanoes because Mesoamerica has volcanoes and you can't explain the geological events in a Mesoamerican setting unless they were caused by volcanoes. IOW, you have to see a volcano in the text. I've read the text many times, but in over 1,000 years of history, not a soul mentions volcanoes. To me, this is evidence that the setting could not be Mesoamerica. The volcano claim is really another example of adding things to the text (#1). To me, we need to find a place where every geological event can take place (even better, has actually taken place), but without volcanoes. The other sciences end up the same; i.e., they point me away from Mesoamerica.
Definitely, there is evidence of Mayan culture in Mesoamerica. Archaeologists continue to make discoveries of new sites and new finds in old sites. Linguists can read the Mayan script or hieroglyphs. But none of it is related to the Book of Mormon. Mesoamerica is considered one of the three main places where writing originated, along with China and Mesopotamia but Mesoamerican languages did not come from Hebrew or Egyptian, the languages mentioned in the Book of Mormon. Outside the bias-confirmation published by the citation cartel, you don't find articles that connect Mesoamerica to the culture or people described in the Book of Mormon.
By contrast, early anti-Mormons (and some modern ones) accused Joseph Smith of simply writing about the Native American Indian cultures he was familiar with because the text refers to "heaps of earth," ancient mining of ore, piles of dead bodies covered with a shallow covering, and much more, all of which are present in North America. Nowhere does the text describe pyramids, or even stone buildings. No jungles, no jade, no jaguars--nothing Mayan, really.
So I can think of two reasons why BMAF has never produced actual evidence. First, there isn't any. Second, they're withholding it for some reason.
I've engaged with evidence-oriented comments on this blog and I've addressed evidentiary issues in the books and articles. If BMAF thinks I've overlooked any substantive evidence, let me know and I'll get around to it.