An industry that is 5% of GDP is a little too much to just give entirely away to foreign competition.  The world wants to buy vehicles of some sort; you better have a way to make them.
No problem. just expand the existing Japanese plants in Ohio, TEnnessee, etc.
Do you have any data to support the claim that auto manufacturing is 5% of GDP? It may be, but that does sound a bit high to me.
(GM sales: $193B) + (Ford sales:$178B) = $371B

US GDP = $11,750,000,000,000

So Ford and GM = 3.2%

I gues if you added in Chrysler and the American components of foreign firms manufacturing here that would bring it to 5%.

Plus you forgot AC Delco / Delphi, Philips Magnavox, Direct TV... to name a few under GM's vast umbrella.