This is much less common than it used to be, but there are still a few such people out there. Apart from the Cumorah-denying LDS scholars and educators, I think most members are rejecting the Mesoamerican ideology. Or, more accurately, I think most members never really believed it. Hardly anyone sticks with Mesoamerica when they understand it relies on the two-Cumorah theory.
Ask around and see what you discover. Ask fellow students or ward members. Most of them will say they've never heard of the two-Cumorahs theory, and they will say it makes no sense.
And that's before they read Letter VII.
The Cumorah deniers claim to have an abundance of evidence. "Look at all the books and academic articles," they might say.
Piling up confirmation bias might look impressive, but when you analyze each piece, you soon discover it doesn't hold up on its own. It's the accumulation of "evidence" that seems convincing, not the significance of each piece (most of which no one has taken a serious look at).
My favorite example is Mormon's Codex, the 826-page book published by Deseret Book and the Neal A. Maxwell Institute for Religious Scholarship at BYU. It has a Foreword by Terryl Givens, who writes, "John Sorenson has again upped the ante with what will immediately serve as the high-water mark of scholarship on the Book of Mormon." That's a fair statement regarding Mesoamerican Book of Mormon scholarship, but when you actually read the book, the entire thing is based on circular reasoning and bias confirmation, starting with the unexamined premise that the Book of Mormon could only have taken place in Central America.
Cumorah deniers might say, "Look at the artwork on lds.org. Look at the Visitors Center on Temple Square. Look at the illustrations in the missionary and foreign-language editions of the Book of Mormon." Of course, this argument seeks to imply that the Church has embraced the Mesoamerican argument, which is not the case. Instead, it reflects the ongoing influence of the LDS scholars and educators who promote the two-Cumorahs theory and have trained most of the people at Church headquarters who are responsible for these presentations.
Another common rationale for believing the Mesoamerican theory is this classic: "All the scholars agree with the Mesoamerican setting."
First, the statement is simply not true. More to the point, when you look at the actual evidence they offer, there's not much there. And what's there is all confirmation bias.
1. 1842 Times and Seasons articles. Some Mesoamerican proponents will tell you that Joseph Smith said Zarahemla was in Guatemala, or that the Nephites lived there. We now know this was a mistake in Church history and informed Mesoamerican proponents have dropped that argument. But the argument has been around for decades, so it will take a while for it to disappear completely. (Some Cumorah-deniers who know better still use it, I'm told, so be on your toes if you attend one of their presentations or hear it in a classroom somewhere.)
2. Narrow Neck of Land. Most Mesoamerican proponents will say that the only place in the Americas that is a "narrow neck of land" is Central America. This claim has arisen from a mistake in reading the text. The "narrow neck of land" appears in exactly one verse: Ether 10:20. Some people have conflated the term with others, including the small neck, narrow neck and narrow passage, but that's not what the text says. The entire hourglass shape you see all the time on the maps is pure confirmation bias. One proof of this: the Mesoamerican proponents have many different interpretations of the geography passages. There's no consensus even among Mesoamerican proponents about anything. Not even Cumorah. You'd think, when their interpretation of the text is designed to fit Central America, that they would reach consensus among themselves.
So far, the only two things on which Mesoamerican scholars have reached consensus are:
(i) that Cumorah cannot be in New York, because, according to these scholars, Joseph and Oliver were ignorant speculators who misled the Church when they said Cumorah was in New York and
(ii) every prophet and apostle since Joseph and Oliver who has spoken about Cumorah has been perpetuating a false tradition, including President Marion G.Romney in General Conference in 1975.
3. Correspondences. Lately, the Mesoamerican theory has boiled down to various "corresondences" between Mayan and Nephites/Lamanites, or Olmecs and Jaredites. Everything in this category qualifies as pure confirmation bias. These "correspondences" involves elements of human society that are common, if not ubiquitous, around the world and throughout time.
This focus on illusory correspondences is one of the best examples of confirmation bias you will find anywhere.
Confirmation bias is everywhere around us. It explains why people looking at the same evidence can disagree about religion, politics, science, and which Star Wars movie is the best.
Confirmation bias is also the reason why facts do not persuade most people. "Don't confuse me with the facts" is not just a funny commentary on human nature. It's an implied sentiment most of us feel toward facts that contradict our beliefs.
There is probably no set of facts that will change the mind of some Cumorah deniers.
Psychologically, they simply cannot find a place for facts that contradict their beliefs. It is evidence of the power of Mesomania, implanted at a young age.
Other Cumorah deniers might change their minds once a certain amount of evidence has been accumulated. For some, Letter VII alone suffices. For others, it's learning that Joseph Smith had his own scribes copy Letter VII into his personal history that is persuasive. For yet others, the many reprintings of Letter VII and the ongoing endorsement by modern prophets and apostles is important. Others might find the archaeological, geological, anthropological and other evidence is persuasive.
The point is, it may be literally impossible to change the minds of every Cumorah denier.
And that's perfectly fine, so long as they have all the facts.