The US spends nearly double what any other OECD country spends (apart from Switzerland, where it still spends half again as much).
Double.
Part of this necessarily goes towards the profits of medical insurance companies - which would be eliminated under a single-payer system - and part of it is the result of being
prohibited from negotiating prices.
However, one of the neat things about migrating towards a single-payer system is it creates what is called 'monopsony power'. If you're familiar with a monopoly, that's a single supplier of products; it effectively has price-setting power. What people are less familiar with is monopsony, a single
consumer of products; this
also effectively has price-setting power, by virtue of telling suppliers 'I buy at this price and no higher; if you don't like it, there's nobody else to sell to.'
Any notion that Medicare For All will be more expensive is ludicrous. It gives more negotiating power to the single-payer, it removes the
pure cost factor for no additional consumer benefit of profits for medical insurers, it eliminates the oceans of compliance paperwork - adding costs - from hospitals' accounting departments...
The
absolute worst-case scenario is that your insurance premium stays the same and you just pay it to Uncle Sam instead of UHC or Blue Cross Blue Shield. The much more likely scenario is that your payroll tax contributions go up - but the cap on those contributions is lifted, meaning the highest-income earners pay in a significantly larger proportion than they're paying now - and you don't owe
anything in monthly insurance premiums, copays, deductibles...
I'll happily talk about policy stuff. It was kind of my field of study, and is at present the field I'm still trying to get a job in (and will keep doing so until I give up out of despair and resign myself to the underemployment endemic in our generation).