The conclusion that AUSTRALIA of all places has a lower SWR (and that Australians should follow it) just goes to show that people have not read the papers and thoughtfully LOOKED AT THE FIGURES.
The following is all my recollection of figures, but I believe that they are accurate enough for the current thread.
My recollection is that the Australian SWR (of about 3.8%?) is based on TWO POOR YEARS IN 1965 and 1966. Similarly, very low SWRs, such as Germany's are also based on only a FEW POOR YEARS. On the other hand, Japan, deserves its low SWR because it has had continuous (more recent) problems.
The wonderful achievement of the US to have the highest SWR should be treated as an anomaly, rather than that they currently have world's best practice. Unfortunately US practices caused the GFC. Because of our banking system and our government's response to the crisis, Australia largely avoided the GFC (and now has the world record for quarters of continuous GDP growth EVER by ANY country), so if Wade Pfau's studies were done in 10 years time, rather than almost 20 years ago, they would probably have quite different SWRs for different countries, and the US SWR would no longer be the highest.
Also, since the second world war, accounting, banking and sharemarket practices have changed radically. As such, I think that the pre-WWII figures used in long term SWR calculations are somewhat suspect. I also suspect that the technology revolution that we have all lived through, the overtaking by China of the US as the world's largest economy and other groundbreaking changes to world economies are changing things considerably. One only needs to think that in 1900, Argentina and Australia had the highest standards of living in the world, and in 2000 that had changed considerably, to realise that the world order of nations isn't stable, and that SWRs based on 1900 - 2000 will be completely different to those based on 1950 - 2050 or 2000 - 2100.
That being said, as others have commented in this thread, when you invest, you shouldn't have all your eggs in one form of investment, and you should have international exposure. The US doesn't make up the vast majority of world productivity, and US investors, like those of every other country, should have a reasonable amount of their assets invested internationally. Some home bias IS worth having, especially if you don't go overseas or buy anything produced overseas, because the majority of the goods and services you buy will be from your own country, in your own currency. In Australia, which has 5% of world productivity, people are encouraged to invest 40% at home and 60% internationally. If the US has 50% of world productivity, maybe you should be going for and 80/20 split - or getting the international exposure even greater.