According to this chart, making what I make in the US, I'd be paying about 28% of my income in taxes. In the US, I pay about 17%, combined, to the federal and state governments, but health insurance costs about another 3% of my income (a portion of which is usually, but not always, paid by the employer, but that's still money paid privately). In addition, that health insurance does not pay 100% by any stretch of the imagination. Every time you see a doctor, it will be at least another $20. Medications cost $5-$30 per prescription per month. Large procedures are not covered very well. (I just had a dental crown put in. They paid half, but that's still $400.) I doubt you could go to an emergency room for less than $500.

I guess if you're healthy, you come out ahead in the US. If you're not, I'd say you come out ahead in the UK. But all of that, as has been pointed out, assumes you're completely indifferent to everyone else's health.