I highly doubt the statistics behind those numbers, is that a typo? Comparing those values thats like $2,900 vs $48,000. How can Japanese have more savings than the Americans when the average salary for the US market is much higher?
The Japanese are truly innovative people and probably why they are one of the first to adopt bitcoin and cryptocurrencies.
You should not judge it based on salary, they might have more salary than japan, but the cost of living might be lower in Japan than US which we know how extremely expensive that living in the United states could be.
The statistic may not be wrong really because I have seen many countries there where I have some friends that are seriously complaining of payment so much for living in the country, and the thing that kills them more is taxing, some countries tax is very high that when they pay you your salary, the amount that is leaving for tax is more than 30 percent of the salary which is very bad. My country is even worst, tax is not imposed on us, but the cost of living is far high that what we learn which makes it difficult for us to be able to save.