Now that I think about it, when I was a kid I used a capacitors to eliminate electrical noise in my AM and SW radios. What are the chances a big-azz capacitor could fix the problem?
That can certainly help if the noise is coming in through the radio power feed.
It won't help if it's just RFI emitted by something else.
I was behind an electric bus a few months ago, and the RFI was enough to take out a weak AM station. There's one intersection I drive though most work days that has a lot of RFI from the traffic signals (I think) that wipes out the weak AM stations. Lots of other noise making devices along the roads, LED lights, signs, etc...
This isn't a technology issue. It's purely a cost savings issue. It cost money to fix the problem. Most of the industries here are more concerned about shareholder profits than they are anything else. Look at the mess Tesla is making with their auto-drive function and all the accidents. It's obvious that they are not concerned about safety.
The feds pushing this is probably the best approach. The auto makers are not going to address it if it even cost them only 1¢ per vehicle. They'll do the absolute minimum possible. Getting this forced will make them look at the issue and actually fix it.
Consumers want the latest/greatest, and they want it at rock bottom prices. I'm betting if you asked most of them, they wouldn't understand what AM radio is, or that it was missing from their vehicle. Probably very few care as they don't listen to AM radio and wouldn't see any benefit at all in having it. The unlikely event they'd rely on it in an emergency would probably not be a concern.
To be honest, I think we are looking at very fringe cases here. Most probably don't care that AM is missing from their radio. Lets face it, AM radio is, for the most part, a total wasteland. Most consumers wouldn't even care about EAS, and would assume their cell phone would tell them what they need. They might be wrong, they might be right, but I doubt they care. I doubt there would be any huge fall out from this not happening. People will adapt...