The comparison of the statement that “there were some cities which remained” with the statement that “the face of the whole earth became deformed” is important. The face of the earth is the surface, and with roads being broken up, and cities destroyed, there were clearly changes throughout the lands southward and northward. However, cities did not change location (save those that were submerged). The land southward did not become the land eastward. Thus, the fact that there was great destruction should not suggest that it would be impossible to discover geographic information about the Book of Mormon. Mormon himself appears to understand that he can describe a geography before the catastrophe and that it would have meaning to those who could recognize the locations.
Of course, there are many possible locations that have been proposed for the Book of Mormon, and discussions over the different models will continue. Still, the idea that there were so many changes that we cannot discover anything about geography doesn’t fit with the reality behind this type of natural disaster.