“Will Detroit stand for this?”
They won’t have to.
The US will not accept that deal in isolation.
It could be an element of a much broader deal, but only if the broader deal brings balance.
Trump has threatened a 25% tariff on German cars. That threat was made isolation. They respond by offering no tariffs if Trump will do the same for the U.S. If Trump doesn't accept then it makes his claim to want a tariff-free world to be a fraud. If he does accept it then he probably loses Michigan. The Europeans are trying to put him over a barrel.