Don't take this as I'm not for universal healthcare because I am in general, that said health care is an insanely complex system that can't be simplified down to 'taxing the rich' a bit more.
I'm not sure how much money you think Amazon and those big companies make but even if you took every dime they made you'd still not be anywhere near enough to implement a single payer healthcare system in a country the size of the USA. Even if you made radical changes to the system the average citizen would have to shell out a lot more tax.
Heres a quote, you can find all of this information with 10 seconds of googling.
'The United States spends more on health care than any other country in the world, and a large share of that spending comes from the federal government. In 2017, the United States spent about $3.5 trillion, or 18 percent of GDP, on health expenditures' <- This is in the current system, imagine what that number is if it was all paid by the government.
Amazon had approximately $280 Billion in revenue last year (not profit, just revenue). Looks like they made about $10-12 Billion in profit, it would be a drop in the bucket to just tax them more.