Dumber than a box of rocks! "American made" cars are not 100% sourced, fabricated and assembled on US soil. Few products are these days. Even if auto companies wanted to, it would take a great deal of money and time to get all the thousands of parts that cars are made with truly Made in America.
The global economy that now exists has escaped his notice in his haste to have Americans fund his needless Tariff Wars.
Tier One auto suppliers were struggling and closing US plants 20+ years ago. Cars may be assembled in the US, but many parts, such as transmissions, are made in foreign nations. Duh!