I don't think tbis quite holds - money being spent on domestically produced vehicles should be going to working families, so the money stays and is spent again in the country. Now if most of that money just goes to the mega rich, then it's fairly pointless.

But it's definitely more complex than just money saved = money spent elsewhere

I agree with this. It certainly is more complex than just that. Only yesterday was I thinking about this topic, as I was walking around Osaka and looking at the cars over there. I would like to see an actual study on this question.