This line shows us about the man-made. Both the jar and the borders of the state of Tennessee were conceived and made by men. Thus, the idea of Tennessee symbolizes men trying to control nature.
It made the slovenly wilderness Surround that hill (3-4)
Here, the wilderness is contrasted with the man-made. Except, "slovenly" is a pretty man-made word to use to describe the wilderness. Things that are neat and well-kept—in other words, far from slovenly—are normally the way they are because a human has made them that way. So, the wilderness is being distanced as far as possible from the man-made, even while it's bowing to the will of this little jar.
The wilderness rose up to it, And sprawled around, no longer wild. (5-6)
Again, we see the jar exercising control over the wilderness. We can almost imagine the trees like subjects of the court, all bowing down at once to pay homage to the king—in this case, a jar.
The jar was round upon the ground (7)
Terrific. Even though this jar commands the wilderness, it's so boring we can hardly stand it.
It did not give of bird or bush (11)
Ah-ha! So the wilderness has something the jar doesn't have after all. Things in the wilderness can breed and grow of their own control. You could trap a baby bird in a jar (but don't, guys, that's cruel), but you certainly couldn't create one with a jar.