Who are these people that are actually happy with their current plan? Dealing with insurance companies is one of the most painful experiences you can have. We have massive out of pocket expenses before they cover anything $4k+, then there is a absurdly confusing system of what is covered and not, and hours of phone calls to figure out what's going on. Then we get multiple bills from the hospital, saying it's not covered, when really it is (this seems like a scam! Hoping we'd just pay!), more hrs of phone calls etc. And for all this my employer pays over $10,000 per year! Which of course comes out of my salary. No it's not "subsidized" by the employer, it just increases the cost the the employers so lowers your salary.
So that premium alone is more than a 10% income tax right there! Including the deductible it's over 15% in "tax"! And every study says the US pays the most, with the worst outcomes. So by any measure I'd have to get a lower "tax" with a government system, yes please! There is no way a government system wouldn't be cheaper for at least 90-95% of the population, every employer (especially small ones), encourage startups, reduce waste, simplify healthcare, etc etc. The only loosers would be insurers, and maybe the top 2% richest. This really isn't debatable, it's just facts.