30 million without even decent care, many with insurance that avoid getting treatment due to co-payments, many that go bankrupt due to cost of health care, many that work like slaves due to fear of loosing work (= loosing health insurance for family), opioid crisis... yes the system is nearly perfect so why change.
Also size argument is really stupid. Universal health care works well in big countries - Japan, Germany, UK (OK, mostly well), France combined match the population size of the US and they all have it.
The cost of healthcare per capita in the US is like double of everywhere else, so if the system is changed to be more effective there will be plenty of money to not only cover everybody it can even be cheaper.
But really it is better for the rest of us if the US keeps overpaying, since that means the US is really sponsoring much of what the rest of us benefits from when it comes to new drugs and such.