'The Things They Carried' has been described by critics as a composite novel.
In other words, it seems like there are quite a few connections between the various short stories which makes it seem like a novel. Connections like repeated appearances of characters, plot elements, continuous metafictional analysis (that is, in a lot of stories, O'Brien questions how the story should be told and whether he is telling it correctly. What examples of this can you find? What other interesting connections can you find??
I think you are right to describe this collection of stories as an almost composite novel. In a sense, it has more links than some novels that really just give a loose narrative of the stories of different characters and follow them through. Yes, this collection of stories does not have a rigid chronological structure and skips around a lot, but I think many novels have moved away from that approach now.