Comment by _heimdall

The ratio of domestic sales and domestic production has widened over the same period. In 1970 the ratio of domestic production to domestic sales was .933, in 2019 that ratio is .796.

Though we are making more total cars, were making a smaller percentage of all cars sold.

As another commenter pointed out, the cars we make today are amalgamation of parts and design work done overseas. That isn't necessarily a bad thing if you view globalization favorably, but it is another factor when considering the value created in the US with regards to vehicle production.