China can hit American farmers, but their overall trade surplus is $295 billion. The US has much more leverage.
So while tariffs will stop some importation of Chinese goods due to costs others are just going to cost more for consumers until the proposed US manufacturing capacity is build up.
Same with auto parts, even the US car makers rely on foreign made parts and have no real alternatives.
People assume there's going to be massive investments into what is essentially an uncertain market. A reversal of the capital outflows of the previous decades or something, dunno?
Why, exactly, would people from other countries chose to invest in the US when they could just keep their investments at home and/or engage with more reliable trading partners like the EU, South America or Asia?