The auto industry isn’t really an oligopoly though. Even if you restrict to “manufactured in the US” there are more options now than there were 30 years ago _because_ the three big manufactures were making trash, and competition did the job it was supposed to.
> there are more options now than there were 30 years ago
I suppose how true this is depends on what sorts of options you're looking for. The number of acceptable cars on the market now, according to my criteria, is lower than it has ever been.
For instance, there are aspects of new cars that are ubiquitous and I find so objectionable that they prevent me from buying one, probably ever. If the market were more vibrant, I suspect that I'd have real options aside from "I can't have a car".
Also, oligopolies don't automatically mean that the products are improved. Usually, it's just the opposite.