The problem with international diversification is that when the US market crashes the rest of the world follows. So when you need diversification, you don't get it.
I have never found any historical data to suggest to me that holding ex-US equities is valuable, particularly in a FI context.
From the article that you posted:
That grey line, that's my portfolio. And it is even more extreme if you extend it out another three years. EDITed to add: well, maybe not extreme. But grey is positive and blue is negative in real terms.
I'm happy to acknowledge the limitations of the US but I think it's hard for the next 30 years to tilt away from the US. The US is big, innovative, and diverse, with an excellent higher education system. China and India are communistic and corrupt, Europe is entrenched and stagnant. The rest are tiny market caps.
I'm holding US.
You can do whatever you want with your money, but Japan+South Korea+Taiwan is currently something like 9.2% of the total world stock market and just happens to include Samsung, TSMC, and Toyota.
But as the article points out, the dot-com recover is the last time ex-US outperformed, about 20 years ago! (and runup to GFC, 06-08). The 2008 crisis was worse outside the US, and the recovery was slower and not as great as well. Sure I believe in reversion to the mean, but god damn it's taking a long time!
In the 70s-80s some of the recoveries were better abroad, and maybe that will happen again. But that was also before the Euro, and many of the systemic issues the EU is still struggling with, and have since 2008. But as you say an increased % in Asia maybe could help? I do think it's even more connected now than it was 30 years ago, so I'd guess that both down and up US and ex-US will be more in line in the future, but that's just a hunch.