But, as you say, there is a lot of sunk costs in Detroit. Sure, Tesla started up in Freemont. But Ford, GM, and the other big manufacturers are also building EVs. And it is easier and cheaper to retool an existing line than it is to build completely new infrastructure.

But it is very complicated. For example, we have a '98 Jeep Cherokee. USA, right? Well, the transmission was made by Toyota. Was it imported from Japan, or made domestically...I don't know. But we have components made all over the place, different makers, being assembled in different locations. If you think you're buying an American car, it likely has foreign components in it. And it may not have been assembled in the US (and some foreign cars are assembled here). This was the first hit from a quick search:

autoguide.com - Top american cars not made in the US

So they already are a mish-mash of manufacturing. Adding EV shouldn't make that much difference to the mish-mash.