The myth of a 4% safe retirement drawdown rule - International return data shows even 4% maybe too optimistic

It’s widely accepted that a new retiree can safely withdraw 4% of their savings, a 4% drawdown in the first year of retirement and adjust this amount for inflation in subsequent years. Analyses of historical US  return data has shown that this drawdown rate is safe in the sense that the strategy will not lead the retiree to exhaust all of his or her remaining assets for at least 30 years. How safe should you feel about this rule in the years ahead?

According to this study, below even a 4% retirement drawdown rate is too aggressive when it is based on international market returns -
http://www.advisorperspectives.com/newsletters11/An_International_Perspective_on_Safe_Withdrawal_Rates.php

The 4% drawdown rule is based on US financial market returns since 1926, a time period which may have been a "particularly fortuitous" one for the United States. The fear is that using this time period will produce dangerously overinflated retirement drawdown rates if asset returns fail to be so strong in the future. Over the time period mentioned, the US consistently enjoyed among the world's highest inflation-adjusted returns and lowest volatilities for stocks, bonds, bills and inflation.

From an international perspective, a 4% drawdown rate has been problematic. According to the same study as above:

The calculated safe withdrawal rate exceeds 4% in only three of the other 16 countries: Canada, Sweden, and Denmark. As for other countries, the most unfortunate retiree of all was a Japanese person retiring in 1940, whose maximum SWR (safe withdrawal rate) was a miserably low 0.47% as high inflation and low real returns plagued Japan during and after the war. Six countries experienced withdrawal rates below 3%: Spain, Italy, Belgium, France, Germany, and Japan. In Italy, the 4% rule failed 62.5% of the time, and in Japan, such high withdrawals were sustainable for only three years in the worst-case scenario.

Should Americans expect or at least prepare for lower asset returns in the future, such as those that many other countries have experienced?   We can hope that asset returns in this century will continue to be strong supporting necessary drawdown rates, but such assumptions may prove to be too optimistic for current times.