While all states have laws against homicide, they vary in definition. A killing that is self-defense in one state may manslaughter or even murder in another. States decide the definitions and punishments for murder, why should abortion be different?
Deeply, deeply flawed analogy.
There is no state that permits one person to kill another for personal advantage or on a whim.
States may quibble over the exact circumstances that constitute legitimate self-defense, but no state permits anyone to justify a murder by saying: "I didn't like him being around so I killed him."
One could also argue over abortion whether or not an abortionist was in a culpable state of mind, whether or not the pregnancy constituted a direct threat to the mother's life, etc. just as the legal ramifications of all other killings are debated in court and classified into murder, manslaughter, negligent homicide, justifiable homicide, etc.
But it is an enormous jump from debating the merits of particular cases to asserting a carte blanche "right" to murder unborn children.