There's something really insidious about tying 401ks and other retirement accounts to the stock market. People including myself end up with a large portion of our assets essentially gambled on the future success of US corporations. It gives some false legitimacy to this idea that our media is constantly pushing, that if the stock market is going well then regular Americans are doing well.
Further, my 401K allowed for indexes tracking foreign markets, real estate....
I don't doubt that the majority of people exposure to stocks are U.S. markets, to be sure. But perhaps, to that end, the government (Feds) are more likely to respond to collapses in the U.S. Stock market than other forms of investment.
I don't know that I believe it myself, but I'm proposing that maybe the "safe" money is in U.S. Stocks.