Adding up the population[1] (in millions, rounded down) of all countries in Europe with universal healthcare[2], except the 144 million from Russia, which is mostly asia anyway, I get to 484 million people covered by universal healthcare.
This includes countries like Germany (81M), France (66M), the UK (65M), Italy (60M) and Spain (46M), which should alleviate the fear of 'small European countries can do that, but not a state as big as California'.