China has mostly decoupled from the US (both for imports and exports) [1]. They will automate around their demographics issues (they build and install more robots than any other nation in the world) [2]. They export cleantech to the world [3]. What does the US build besides systems of rent seeking?
They'll presumably happily sell all the factory automation to anyone else who wants it (everyone else has), so it's not clear factories will stay where they are long term. Once factories are near fully automated, they'll place them wherever the combination of taxes and transportation costs is best.
Keeping the factories ensures trade continues, selling the factories eats the seed corn. To your point, I think its more likely they build fully automated factories where they want to sell to avoid tariffs or trade barriers, while maintaining ownership.
https://youtu.be/UltVl2Qlf6A