The USA made only 70,000 cars in 1945 but it took off quickly after that. The next year of '46 saw 2,150,000 cars produced! That is an amazing increase. See below for what happened thereafter:
I must say that the production inconsistency surprised me, it particularly fell away in the 21st century. Part of the tapering off is due to Americans turning away from cars to what they call trucks. For example, just under 3.5 million trucks were made in the US in 1985, but 5 million were manufactured in 2010. That does not make up for the car making drop, but goes someway to explaining it away. Still, US car production is lower than most would expect as many are imported, especially from Canada, Mexico and Asia.
So which manufacturer made the most cars in the US in 2010? (answer below)
In summary: Does car making have much of a future in The US of A? Of course, but not in the numbers you may have thought.
Answer: GM 600,000.