That's only true in a perfect globalized market economy. To head you off, I understand the the downward shift of the demand curve when the price level rises, that makes complete sense. However, if the net result of not having protectionist trade policy is a loss of on-shore production and at a later date their is global instability, whether from a pandemic virus or war, such that a global market no longer functions freely, then wouldnt the "expense" be an investment? Demand for cars is fairly elastic I would imagine, so wouldn't domestic suppliers increase production?

Looking at vehicle production through the single dimension of economics without considering geopolitics seems naive.