The title prepares to the reader to be on the lookout for the black cat – it suggests that the cat is important to the story. This might sound obvious, but what if the story was called "A Woman Murdered," or "An Unhappy Home," or "Why I Stopped Drinking"? The first would focus attention on the nameless narrator's nameless wife, the second on the idea of "home," and the third on the issue of the narrator's drinking. All these are important aspects of the story (though by no means the only aspects), and all are connected to the cat (or cats). But, whatever the title of this short story happened to be, the black cat(s) would still take center stage of this tale.
The title only references one black cat. Does this mean there is only one cat in the story? Is the second cat a kind of Pet Sematary version of Pluto? Is the second cat Pluto the undead? Or, is it possible that Pluto didn't really die? In that last scenario Pluto somehow survives the hanging and escapes the plaster cast/wall art (in which we last saw him). Then, either on purpose or by coincidence, the cat meets the man at the place where he's drinking and, well, you know the rest.
We can't neglect the two-cat theory. Just remove the possibility of the supernatural, and assume that Pluto and the second cat are both real, flesh and blood creatures, horribly abused. This reading might even be scarier than a supernatural one.
The story is wide open for multiple interpretations. That might be why "The Black Cat" still popular, over a 160 years after its publication. The title is simple, and straightforward, but we can still use it to open up this creepy story.