Who would be at fault in this car accident?

Traffic law is definitely not my forte, so other lawyer-types can feel free to correct me, but my sense is that this is a matter of "last chance" doctrine. If you could have avoided the accident by stopping, but didn't, then you had the last chance at avoiding the accident and you have at least partial liability for the ensuing accident. (At the very least, the hypothetical other guy could make things quite lengthy, unpleasant and expensive for hypothetical you. My trial advocacy professor always said that there's no case more complicated to try than what looks like a simple traffic case.)

I think Los Angeles is responsible. you could try and sue them.

As a soon to be former "lawyer-type," my analysis would go like this. . . First, we'll have to assume there are no contrary witnesses and both drivers tell the same account (after all, if he's this much of a jerk, just swearing him in isn't going to change his personality, and yes, Virginia, people lie under oath) because he may claim you were cutting into his lane, and at this low speed in congested traffic, there isn't going to be any physical evidence, and no accident investigation. Let's also assume he doesn't claim that he didn't see you there because you were in his blind spot (which you may have been, although we both know he knew you were there). The most likely result in front of a judge is he will be irritated that both of you are clogging up his courtroom, he will view you both as hotheaded "road rage" jerks and find you both guilty of whatever charges are brought before him on the police citations. In a civil suit, he'll probably find you were both at fault. Your insurance companies are going to raise both of your premiums, and both insurance companies will find any way possible to blame their own policyholder, because they're not going to spend the money to sue the other driver's insurance company. The real world practical result is that both of you will end up losing, which doesn't solve anything.

Now the young, single, backslidden, doesn't need to be an example to his children me has all sorts of forms of retaliation I used to use under these circumstances, but I think peggylou and kelly don't want me giving you any more bad ideas for reckless, disruptive conduct. Console yourself that the other driver's conduct is undoubtedly a result of his lifetime resentment with his phallic inadequacies, and leave it at that.