Rhetorical: Alma does not separate temporal and spiritual worlds. He has invoked the very temporal difficulties of the flight from Jerusalem, the journeys in the wilderness, and the conflicts in the New World where the “fathers” were in mortal danger. Immediately after invoking this mortal danger, Alma adds that it might also have included immortal danger.
This combination of factors allows Alma to both invoke the very real histories of conflicts, and emphasize their spiritual meanings. The fear of spiritual destruction is not simply a rhetorical device, however. Had the people of Nephi been conquered by their surrounding world, their understanding of God would have been destroyed (as was that of the Zarahemlaites prior to the arrival of the Nephites). It is this real danger that is Alma’s greatest interest, because it is precisely the danger that the Ammonihahites pose to the greater land of Nephi, as he has noted before.