None of those countries are the size of the US. Just like in Physics, you can't expect a 1/10th scale model to behave the same as the life sized version.
Japan has what...126 million people? So according to your math, America must have 1.26 billion people? Australia is as big as the US if you meant by area, plenty of other countries approach 100+ million besides Japan.
The EU has 511 million people. Sure it is multiple systems, but they all work much better than ours does.
Japan is a totally different culture than America, and their health care system is similar to ours in that it is employer paid. Also, you have no medical privacy rights, your employer gets a copy of every medical bill you incur.
Source, lived there six years and spouse was in that system for over 25 years.
Our healthcare system isn’t employer paid, it also has a large individual market (or those who can’t get access at all).
Japan, unlike the USA, has a health insurance plan for those who can’t get it through their employers (NHI, hence their system is considered universal).
I'm not sure what you mean by "our", that's ambiguous in this context. If you mean US, we don't have a "healthcare system", most health insurance is partially employer paid. My comment was not as clear as I meant it -- I meant that Japan's healthcare system is employer paid, which is similar to how most people in the US are insured. Maybe that's more clear.
Japan does also have NHI, but most are insured through their employers, as nearly everyone in Japan either works or is insured by someone in their family who works.
None of those countries are the size of the US. Just like in Physics, you can't expect a 1/10th scale model to behave the same as the life sized version.