Yeah, I had a similar situation in my 20s, younger kid (6-10?), on a road trip in another country. Nothing that would be individually extreme enough to feel intervention was necessary or that overtly established something else going on the rest of the time, but the vibes were off-the-charts bad and I assumed that, if anything, it had to be even worse away from public scrutiny. The kid was really trying, and honestly was taking it better than I was, just as a bystander, though maybe some of it flew past her. I wasn't in a state to take over driving after that, and it actually kinda messed me up for a few days. I don't think it was a situation I'd have the skill to mediate if I did gather myself enough to jump into it, let alone whether any sort of bystander intervention would have a net positive impact. Still don't know what I would or could do if something like that happened again.