This stuff is so misleading. Most countries with universal healthcare don't have "Medicare for all." Germany, for example, has a system of public health insurance entities with mandatory enrollment of employed workers. It is paid for by a very high (15.5%, split between employer and employee), and rather regressive (only on the first 52,000 euro per year of income) payroll tax. By comparison, the U.S. Medicare tax is just 2.9%, on all income with no cap. No deductibles or co-pays in Sanders' plan? How about France, where most medical care has 30% co-insurance (government only covers 70% of cost)?
His heart is in the right place, but Sanders lives on a planet where if only the U.S. would cut its defense spending down to NATO levels (cutting about $250 billion a year), we could afford to spend trillions more per year on free healthcare, free education, etc. Except Europe isn't a liberal paradise--they have to make ends meet like anyone else. So you get free education in Germany, with aggressive tracking to keep most people out of the educational system after age 16. You get 40% income tax rates on people making median incomes or below, 20-25% VAT that primarily affects the middle and lower classes, but low corporate taxes (because you have to keep businesses around to bankroll the welfare state). There is no major European country that meets the Sanders ideal of offering free healthcare and education, but which encourages everyone to take advantage of those things, and also pays for it by taxing primarily the rich and corporations.