One of the major debates between defenders of the Book of Mormon as history and opponents of this claim has to do with whether the book must necessarily have been intended as a sacred history of all of North and South America.  Apologists for the book’s status as history argue that the text is more compatible with the idea that the children of Lehi were never more than a drop in the ocean in population terms.  On this popular reading, almost the entire Book of Mormon would have taken place in a relatively small part of Central America.  This approach helps make the journeys mentioned in the book more plausible.  It also greatly reduces the ability of DNA analysis to falsify the narrative.

Opponents of a historical Book of Mormon try to reject this
interpretation by pointing out (1) that most Latter-day Saints believe
in the whole-continent interpretation–a fact I consider true but
irrelevant; (2) that Joseph Smith seems to have also believed in the whole-continent interpretation, a more relevant but still manageable objection; and (3) that several revelations in the Doctrine and Covenants identify individuals as Lamanites in ways that seem to require a whole-continent interpretation of the book.

This last argument cannot be dispensed with using the same arguments used against the first two points.  Purely personal beliefs, whether held by prophets, church members, or anti-Mormons, are not binding on anybody.  They’re just opinions.  The contents of the Doctrine and Covenants are, of course, another matter.  Such statements are authoritative texts for Latter-day Saints, accepted as part of the canon and equal in status with the actual text of the Book of Mormon.

An example of the kind of material I’m talking about is Doctrine and Covenants 28:8, which gives Oliver Cowdery the following instruction:

And now, behold, I say unto you that you shall go unto the Lamanites and preach my gospel unto them; and inasmuch as they receive thy teachings thou shalt cause my church to be established among them; and thou shalt have revelations, but write them not by way of commandment.

In response to this instruction, Cowdery led a mission to the American Indians.  Did he misunderstand the revelation?  Was he really being sent to Central America?  Or is this an authoritative identification of Native Americans as Lamanites?

The next verse adds some additional clarity, stating that the city of Zion is to be built "on the borders by the Lamanites"  (verse 9).  Missouri, of course, isn’t terribly close to Central America.  However, it was close to Native American territory at the time of this revelation.  Once again, we seem to have an authoritative identification of the Native Americans as Lamanites.  Similar statements can be found in Doctrine and Covenants 32:2 and 54:8.  In other words, there seems to be a canonical–as well as a folkloric–Latter-day Saint tradition that identifies Lamanites with Native Americans in particular, and potentially with all pre-Colombian peoples more generally.

How are we to deal with this?  One possibility is to conclude that limited-geography theories are out of harmony with the mind of the Lord as revealed the Doctrine and Covenants.  This would , of course, make limited geographies unacceptable and even blasphemous for faithful Latter-day Saints.

A second alternative is to propose that the Doctrine and Covenants not be treated as infallible.  The revelations in the book may instead be interpreted as Joseph Smith’s best human attempt to express the messages he was sent from God–with the understanding that the doctrines and statements in those revelations are a mix of the erroneous human and the reliable divine.  Some Latter-day Saints probably already believe this, while others would likely tend to find it blasphemous in its own right.

The third alternative that I see is to conclude that the term "Lamanites" may have different meanings in different situations.  At some points in the Book of Mormon, the term seems to have had a geneological meaning.  At other points, it had a more social and political meaning.  If we accept that "Lamanites" can have different meanings in different contexts, then the Doctrine and Covenants texts are not necessarily in conflict with limited Book of Mormon geographies.

For example, if we take "Lamanites" to mean, in the Doctrine and Covenants, all pre-Colombians who were not Nephites, then we don’t have a problem.  Of course, in conjunction with a limited geography for the Book of Mormon, this would mean that the vast majority of Lamanites are not descendents of Lehi–and in fact would have had no idea that Nephites or the Nephite religion ever existed.  This seems an somewhat problematic stretching of the term "Lamanite," but that consideration does not definitively rule out the meaning.

Also problematic for this third approach is the existence of Doctrine and Covenants texts that seem to use "Lamanite" in a different sense than this.  For example, consider 3:16-18, which says,

Nevertheless, my work shall go forth, for inasmuch as the knowledge of a Savior has unto the world, through the testimony of the Jews, even so shall the knowledge of the Savior come unto my people–and to the Nephites, and the Jacobites, and the Josephites, and the Zoramites, through the testimony of their fathers–and this testimony shall come to the knowledge of the Lamanites, and the Lemuelites, and Ishmaelites, who dwindled in unbelief because of the iniquity of their fathers, whom the Lord has suffered to destroy their brethren the Nephites, because of their iniquities and their abominations.

This text seems to refer to the different Book of Mormon tribes in a geneological sense.  In particular, Lamanites are said to have fallen into disbelief because of "the iniquity of their fathers," who would presumably have been actors in the Book of Mormon drama–if not direct descendents of Laman.  If the Native Americans of Joseph Smith’s day are required by the Doctrine and Covenants to have been Lamanites in this sense, then there is a serious difficulty for limited geographies.

In a similar vein, Doctrine and Covenants 19:27 explicitly identifies the Lamanites as geneologically linked to the Jews.

I don’t see any problem with the proposition that different sections of the Doctrine and Covenants, which after all contain revelations given in distinct circumstances spread across a number of years, use the term "Lamanite" in different senses.  Hence, these texts do not definitively disprove the hypothesis that "Lamanite" is used in a social and political sense in some sections.  Nevertheless, they do constitute an anomaly for this account.

I mention this material particularly because, while I have seen a few different arguments from advocates of a limited geography to the effect that non-canonical statements should be disregarded, I have never found any such commentary with respect to this Doctrine and Covenants material.  Enemies of the limited geography hypothesis and of Book of Mormon historicity, by contrast, do make use of these revelations.  (See footnote three in the Editor’s Introduction to this famous, or perhaps infamous, book.)  Advocates of the limited geography approach do need to address this issue.  I’ve offered what I see as the three possible believing responses (in broad strokes, of course), so my work is done.