Textual: Nephi returns to his current theme, the delivery of the gospel to the gentiles. In the 1830 edition, there is no chapter break at this point. While the change in topic from the previous verse to this one is certainly sufficient to justify the beginning of a chapter, it nevertheless obscures the nature of the aside by making it less obvious that those verses come as an interjection in Nephi's main line of discourse.
Narrative: That his description of the state of the Jews and Gentiles is true is only part of the point of Nephi's narrative. The point of Nephi's discourse is to show how the words of the righteous of his people will be given to the gentiles, and will be for them an instrument in their conversion to Christ. Thus while it is true that the Christian churches were all in a state of apostasy from the gospel, it is a literary over-statement to declare that they "will be drunken with iniquity and all manner of abominations--." This coloring of the entire world as personally "drunken with iniquity" does not allow for those were genuinely good people.
However, this over-statement is not intended to be descriptive of the individuals, but rather the collective world, and is intended not even as descriptive of the general morality, but rather the state of apostasy that will require the instrument of his people's preserved words to bring them to a true knowledge of their Savior.