So health insurance is a cost ... albeit not the same for everyone, at some companies you pay surprisingly little and that is compensation ON TOP OF your pay...
Other places not.
It's really hard to get good 1:1 comparisons.
Taxes and etc in the US are widely unevenly applied depending on the situation compared to what seem to be 'more' standardized and predictable numbers, services, in Europe.
It’s also very easy to compare even if you are an employee, as health insurance premiums are shown in box 12 code DD of an employee’s W-2. And health insurance premiums don’t vary that much between healthcare.gov and ACA complaint insurance that employers subsidize.
What is clear is that there exists a healthcare expense in life, and so if you are paying for it via taxes in one region, you would have to figure out how much it costs in the other region where it’s not included in taxes to make the comparison more accurate.
You can use this table from the state of NJ to reasonably guess how much healthcare will cost you in a moderately high CoL area in the US:
https://www.state.nj.us/dobi/division_insurance/ihcseh/ihcra...
As for the differing costs of insurance outside of the freelancer world, I've found the costs in the US can vary wildly. Those tax boxes aren't the only way / shouldn't be the only comparison for US healthcare costs.
Some plans will cover some providers and some won’t, and rural areas will have issues with even having providers at all, but for most major urban/suburban regions, it should be comparable, +/- 10%, even 20%.
Either way, you know that healthcare costs are in the thousands and $10k+ per year per family, which is a lower bound you can add to calculating US tax rates.
For example, if you earned $150,000 as a contractor, but you incurred $30,000 in expenses then you would have $120,000 in potentially taxable income.
The tax code is very, very complex, though, and there isn't a simple answer to this question. There are a vast array of factors that would shift how much you pay in tax up or down, and this complexity is heavily exploited by lots of folks.