> why invest in USA when you could invest somewhere where you can import the needed inputs much cheaper?

What markets do you have in minds? Can retail investors invest there?

I foresee something closer to a proportional increase of investment in all the remaining accessible markets, as US relative attractiveness decreases, rather than it moving to a specific other place.

So basically, everywhere else, proportionally. Even markets that have worse import/export restrictions, will still have relative changes in their attraction.

For a rough approximation non-US world index ETFs, which are available to retail investors.