If I leave my door open and someone steals my TV, it's not my fault I don't have a TV anymore.
But that's not what this case is about. To use your analogy, imagine KIA were a lock maker such as Kwikset. You bought their lock to install on your front door. You locked your door and left the house. You came back and your TV was gone, with no signs of forced entry. That's when you discover a major flaw in the design of the lock - if you turn the knob the opposite way then the lock will unlock from the outside. It's a flaw in the design. The lock maker is definitely legally liable for that defect, and, this is the important point, the city of Baltimore could sue them claiming damages incurred by having excessive police calls caused by their defective product. Of course every case is different, but Baltimore would be likely to win.
I'd say they're likely to win in this case as well. Since KIA has been aware of this problem for some time and taken no steps to resolve it, I imagine Baltimore is applying some financial incentive. As other cities take note they too may file their own suits and then KIA may realize it's cheaper and better PR to issue a massive and costly recall.
Now practically, whether it's legal or not, no one is going to help you.
To the extent that common law is generally adopted in the United States, theft is the intentional taking of the property of another with the intent to permanently deprive the owner of said property. It doesn't matter whether there's forced entry or not (you may be thinking of burglary -- either way, principles of "constructive breaking" could still apply depending on the law as codified by a given jurisdiction).
Even from a less pedantic standpoint, if I had a home surveillance system that captured the entire incident on camera (along with the perpetrator's face and the license plate of the vehicle that he used to drive off with my TV), there is still sufficient evidence to arrest and prosecute. There is no legal requirement of "signs of forced entry" to sustain a theft charge under these circumstances.
If the theft was part of a bigger issue with (to use the Kwikset hypothetical) the vendor's product defect allowing mass thefts then it would be important to the police.
This is not correct. The police will take a report, and your insurance (if you have it) will cover your TV even if you left the door wide open. Even if you were drunk. Even if you weren't drunk. There is no clause in standard insurance policies or our laws and statutes that failure to lock shit up somehow makes it free for anyone else to take.