Very few American comic books sought to go beyond purely episodic stories until the mid-1960s, when Marvel began making its storytelling mark. Some of the "long arcs" at Marvel resemble simple film-serial cliffhangers, but others may have been more influenced by the narrative example of American comic strips. This online essay asserts that post-WWII Japan was definitely affected by the importation of newspaper strips, though of course there may a host of other factors that influenced the country's fascination with long, involved story-arcs. It's possible that, while the American comic book remained strongly wedded to the short story, Japan made greater strides in the realization of the "novel in graphic form," simply because they had no preconceptions against the idea.
Now, in earlier essays like this one, I've asserted that narratives have 'had their greatest capacity for mythicity when they possessed the traditional "beginning, middle and end," which worked to maximize a given story's potential for "connotative associations."' However, the majority of "long melodrama" comic strips of the classic period lack the scope of the novel in terms of such associations, because "each of these story-lines is just one narrative arc, without a lot of complementary development,"
I certainly wouldn't say that all of the long multi-chapter arcs in manga are necessarily better developed than those of the best classic American comic strips, but the potential has generally been better realized, perhaps because some Japanese authors have emulated the intricacies of the prose novel. At present ONE PIECE has not yet concluded, so it can't be judged in its entirety, but Oda has often laid down involved plot-threads in one sequence that would not culminate until a much later sequence. Whether or not Oda's execution of those plot-lines proves felicitous or not is a separate matter; he's using novel-like narrative devices that were only very rarely utilized in "long melodrama" comics, with an occasional exception like this DICK TRACY sequence.
This week's mythcomic will be DANCERS IN THE VAMPIRE BUND, which boasts a heady complexity of plot and character. However, the original 14-book sequence of BUND, completed in 2012, was something of a novel-fragment. Two years later, the author came forth with SCARLET ORDER, a four-volume follow-up, which might be loosely regarded as the "end of the novel" (although some plot-threads were not resolved, and were certainly intended as lead-ins to further tales). Despite its heavy fantasy-content, BUND is written largely like a political thriller, and this raised the danger that the author might have created too many characters and story-arcs to allow for a reasonably clear "beginning, middle, and end." However, I'm pleased to see that there is a sense of resolution in SCARLET ORDER, so that I can finally put the series on my list, after having alluded to its potential excellence back in this 2011 quasi-review.