I will preface the following by letting you know I am not a lawyer though I have a fair amount of experience with trials, lawyers, and the USA legal system. I am quite aware of how easy it is for collusion to occur unintentionally- I was a victim of that myself. A person witnessed my situation only after I reacted, then told the belligerent how he'd seen me start it and the bad guy, seeing a way out followed along. I ended up being prosecuted for legally defending myself because it was two "witnesses" against one. This had a lot of bearing on why I bought a dashcam, for it is the ultimate unassailable witness and no amount of lies or liars can overcome it.
In the US the laws vary so much by location that you must always check locally. In most places, any audio recording made without the knowledge of all parties being recorded is inadmissible as evidence. Consent, either direct or implied may also matter. It may be illegal to record them at all. However the intent of the recording matters so you record the events only as a "personal journal" to be having a record of what YOU said, all the other voices are incidental- this makes it legal to do. While it may still be inadmissible in court, it can prove what was said before Court proceedings occur (such as police investigations and prosecutor-defense attorney conversations). That is where many legal-related decisions are made, so while it may not be legal as evidence it can change how trial proceedings go or even cause charges to be dropped, filed, or changed. As always, never reveal anything to anyone except your lawyer, then let them decide what to do with it- they know how to best use it in your favor.
Like your video recording, what an audio recording shows also shows what you did, and that is not always a good idea. If some idiot hits you and you yell "WTF?" or show anger (which is a common and normal reaction) then they will twist that into your being angry and belligerent which will not bode well for you in court. Being someone who mutters about the idiot drivers when I'm driving alone I have my audio turned off, for I know how it can be twisted against me by any decent lawyer. It does not matter that what I say is true; the thing which matters most in a courtroom is how the Judge or jury sees things and that is what lawyers work with. The only one in the courtroom who cares one iota about truth and justice is you and you're outnumbered from the start.
Most of you will have never had to go into a courtroom for more than a traffic ticket or accident proceedings so you haven't seen the deeper workings of the USA legal system but you can trust me when I tell you that you that if there is anything which might make you look like anything less than an angel you'd better keep it so well hidden that they cannot find it or it will go badly for you even when you are totally in the right. In a US court of law the best actor or actress wins; truth and justice have no value there anymore. Your dashcam video alone is enough to prove that you did no wrong, don't go risking the loss of such a good friend by tying it into something which might cancel out that goodness.