I prefer sticking with the text and not adding words. Explanations are fine, but when one has to change the text to fit a geography, the process is backward.
That said, what is a "mountain" in the Book of Mormon?
For now, I'm not even going to consult Websters or Oxford or Hebrew. Just look at what Section 117 says.
So far, I haven't come across a "Two Adam-ondi-Ahman" theory, but maybe someone has proposed that. In the meantime, it seems pretty clear that Adam-ondi-Ahman is the site in Daviess County, Missouri, along the Grand River, 70 miles north of Kansas City. Here is a nice photo looking down on the plains in the valley:
The site is mostly a valley, with the high points being Spring Hill and other hillsides. This type of terrain is common to the Midwest, from this part of Missouri through Illinois, Indiana, and Ohio. These are the kind of "hills" and "mountains" from which armies of robbers could "sally forth." 3 Nephi 4:1. [Note: the Oxford English Dictionary defines the term "sally" as "a sudden rush (out) from a besieged place upon the enemy; a sortie." It can also mean "a sudden start into activity." It's difficult to conceive of how an army could "sally forth" out of high mountains.]
In Central America, Sorenson claims the narrow strip of wilderness "correlates with the band of peaks at the head of the Grijalva River basin along the present Guatemala-Chiapas border (including the volcano Tacana, Central America's tallest peak.)" I'm not sure how an army would "sally forth" out of this kind of mountain.
Bottom line, if Adah-ondi-Ahman has "mountains," so does Illinois, Indiana, Ohio, New York, etc.