Ammon credits righteousness to God, and then notes two positive effects of their missionary works. The Lamanites have been converted to God, and they are no longer enemies to the Nephites. Interestingly enough, it is this latter point that he mentions first. Of course if he is listing things in order of their importance, it is certainly of greater importance that the Lamanites have been converted to God. The mention of the former is the question.
It would appear that they are part of the same point. While there were thousands of Lamanites converted, clearly all of the Lamanites were not converted, and certainly not even a majority of them. There were clearly enough Lamanites left with hostile intentions to sack Ammonihah after establishing themselves in the city of Nephi. The conversion of even these thousands of Lamanites will not make a significant change in the Lamanite-Nephite hostilities. Why then does Ammon make the point that one of the changes was that the Lamanites “would still have been racked with hatred against us.”
It is most likely that Ammon is indicating that without the Lord’s intervention, the hatred would have prevented the Lamanites from hearing their message. This would have been extremely clear to Ammon after his initial encounter with Lamoni’s father on the road to Middoni, where he not only endured the verbal wrath of Lamoni’s father, but experienced the hatred in hand to hand combat (see Alma 20:13-16). Ammon clearly understood that it was the softening of the hatred that began to open hearts to the message of the Lord, a message that the Lamanites might not have been willing to hear, if only because of the nationality of the messengers.