I don't doubt that . . . but how do they know?
Show me someone who regularly deals with both systems --- not someone who spent the previous decade in one system in the current decade in another --- and I'm all ears as to what he says. But most people only have the point of reference of their own system, plus a few selected anecdotes (usually negative) of the places they deem worse.
I worked in Singapore, Japan and China enough to have experience in the health system. I spent enough time in France to know people who have experience in both systems. This all within the last twenty year.
I was admitted to the best private hospital in Beijing. I assure that you should stay away from doctors in China.
I wound up having surgery in Singapore and once went there from China for consolations. The doctors in Singapore seemed to me to be fine and the medical care excellent. I don't know anyone else who had experience with both the American and Singaporean models.
I have afib. In Japan I went to a cardiologist who had done internships in New York and Houston. He seemed fine. He practiced at a teaching hospital. People complain about waits in the Japanese medical system but I don't ever remember waiting more than a half hour. The Japanese cardiologist had Saturday appointments and charged me the equivalent of $30 a visit.
I knew Americans living in Japan covered by the Japanese health care system which I was not. They complained about long waits but on the whole they preferred the Japanese system because of the lower costs and not having to deal with the American insurance companies, networks, et.al. and the Japanese doctors seemed fine.
I do not have direct experience with the French medical system but I know French residents who have lived in the States. They prefer the French system because the care seems at least as good as in the USA. They did complain about waits. But they did not have to deal with the American private insurance system. I have never met anyone who likes dealing with American medical insurance system.
And I can assure you, that from my experience in Singapore, Japan and France that American surgeons really, really like to cut. I had one unnecessary surgery in the United States that Japanese doctors basically believed violated the Hippocratic oath.
Also, my wife is a native of Mexico. She has numerous relatives living in the States. She has had dual citizen relatives who are not eligible Medicare return to Mexico when they are diagnosed with cancer to be treated in the Mexican public health system. They did not seem to believe Mexican is better but they want to protect their families from financial distress.