Because they have higher tax rates. Some people argue that the tax rates are actually equivalent to the US, but that only factors in income tax and ignores VAT (which the US doesn’t have at a federal level).
The claim was that a mere 100 billion would pay for it, proving that claim false does not affect the fact that other countries have it.
“The universal healthcare model is cheaper than the US model”
By about 10 percent. The problem with a lot of analysis of Medicare for all plans is that they assume that it would be able to run at the same cost ratio as it does now. But Medicare currently does not pay for the full cost of services, it’s essentially subsidised by the private insurers. Replacing private insurance would require increasing the Medicare payout percentage or else hospitals would lose money, and have to cut services.
Additionally if you actually poll the public, they do not want to pay the additional taxes to fund this universal healthcare. The US is in a weird position were a chunk of the population has government insurance, but the bulk is pushed onto employers and that’s basically the best place to put it if you want to minimise the burden on the public.