There are probably multiple layers of feedback loops going on, who knows how things will pan out. There's a sufficiently large enough pool of investors out there that will buy broad ETFs like SCHB, SPY, VT, VTI, etc., on any dip or just continue to DCA a little of every paycheck into those just due to its history. The US is geographically isolated from potential threats for the most part unlike Europe and Japan, is relatively self-sufficient, super diversified and lots of international exposure, and no country has as much clout on the international stage as the US for the time being so I think it makes sense the US continues to do much better. Sometimes you have trends like emerging markets, cryptos, etc., but broad US stock market seems like the default choice for high returns so long as there is capital to be allocated.

Interest rates are the thing I think could change things, but who knows. If you can get a guaranteed 5% return that's pretty nice, but it's possible we just slide into being a more corrupt/untrustworthy country for investments or baby boomers suddenly taking a disproportionate amount of money out of the market as they retire, etc.,.