Can you provide evidence for this? I was under the impression that price is dictated by long-term underlying company value. That is to say, time-discounted, risk-adjusted dividends, including buy-outs. Dividends are just paid out via stock-buybacks these days because the dividends are taxed more, despite them being functionally equivalent.

It's true that price is determined by long-term value, but long-term value isn't sorely dictated by dividends. Expected price appreciation itself is a factor for growth stocks. Growth stocks include some very large companies, including Google and Facebook.

Earnings is seen as an indication of future value (and future dividends if it is an income stock rather than a growth stock)

https://finance.zacks.com/profits-reflect-stock-prices-8263....

The value of any stock (or bond or other financial asset) is its expected future cash flows discounted back to the present at a rate that reflects the risks associated with those cash flows. This is corporate finance 101. Higher taxes for US companies means lower cash flows, and lower values for those assets, unless the discount rate is lowered enough (e.g., lowering interest rates further, even going negative) to compensate. Companies with more US exposure will become less valuable, and money will flow to other assets, including bonds, foreign stocks, etc., to reflect the shift in value.

Indeed, this is a good point too. 401K managers are aware of this and can just shift allocations.