Of course the problem is that California is one of the largest markets. If they were their own country, they'd be the 5th largest GDP (not counting enormous ca.gov debts...) So it becomes a race to see which blue state can set the strictest standards, and then if they're big enough, the corporations will comply.
On one hand we have the ICC and the 10th Amendment being abused into obscurity, OTOH, it's kind of like the electoral college, where I don't want California "may cause cancer" and emission standards defining what I can buy and use in Wisconsin either.
And the automakers saying they're cool with CA's regs, I'm skeptical. That smacks of corporatist rent-seeking, and them figuring their competitors might not have a way to handle the regs. And other things, like pushing tons of EV's when CA is going around shutting down every power plant they can, and even with growth, the grid not being able to handle a majority of passenger cars being EV's either.