Yes, I know; but we're talking about what would happen in a hypothetical world where US R&D innovation mostly stops happening, not for lack of money, but for lack of talent; so US investors no longer have any interesting domestic options that are likely to bear any fruit at any multiplier they'd be interested in.

Sure, investors could just park their money in what few dumb domestic options there are. That's the "patriotic" approach, and in less-aggressive markets, you'll see some investors [esp. big institutional investors] building the hedge parts of their portfolios out of these kinds of investments. But when the only domestic options are dumb/boring, any "smart money" investor will either take their money and leave the country for greener pastures, or they'll pick up the skills required to play in foreign markets.

So in this hypothetical, there is zero native US talent?