Earlier quoted context omitted.
The same type of argument can be made about bonds and even cash. And if a diversified portfolio of US stocks all suddenly go bankrupt, that probably means the US is toast and therefore bonds are screwed too. Outside of catastrophic black swan events, like I said, stocks generally mean revert if you have a long enough time horizon to allow it
This is almost the definition of technical analysis: “chart always reverted to mean so it will always revert to mean” Note that almost every exchange outside the US has been flat or negative for decades. The US has held a precious position for a few generations that’s made “chart go up” feel like a given
As someone who works in finance this struck me as a remarkable claim. Upon inspection it turns out to be spectacularly incorrect. After adjusting for inflation it's actually the opposite, the vast majority of countries have seen their own version of the S&P 500 grow over a 30 year period, after adjusting for inflation, not stagnation or decline. Developing countries, particularly those in Asia, have seen incredible returns over a 30 year period, albeit with a great deal of volatility involved.
Our neighbor to the north, Canada, has seen gains that are slightly below the U.S., but our neighbor to the south, Mexico has seen about the same growth as our own, once again accounting for Mexico's own inflation.
Europe has also experienced a great deal of growth with many European countries even growing moreso than the U.S., for example Germany.
While there are examples of decline, they are in countries that are both poor and have unstable governments. Most countries that are strictly poor but don't suffer from instability have for the most part seen growth rather than stagnation.
So I don't know exactly what led you to believe your claim that "almost every exchange" has been flat or negative, but it's certainly not correct.