All arguments about the legality and Constitution aside, I think part of what you're seeing behind some of the arguments here against a national health care system is just plain mistrust of the government. I'd be happier to have a lighter hip pocket for others' medical care if my pocket hadn't already been lightened for numerous other reasons. US debt is high (60% of GDP today) and getting higher (expected to be 100% of GDP by 2015 by some estimates). Congress has shown plenty of interest in spending tons of money and not much interest in balancing a budget. There's a limit to how much we can cough up, and the expected costs of a national health care system just speed up how fast we expect to go further into debt.
Seeing responses here from people who live with a government health care system has certainly given me reason to think harder about it - I was very much against it at one point, partly because of reading horror stories not only in the US press but even in other internet-accessible media outlets in other countries. But, hearing from live people here on Mobileread who don't see those same problems occuring helps quite a bit to ease my mind about the concept.
It still remains though, that we have a huge and growing deficit. (Yes, the military budget is one reason but there are many others.) We have several federal health programs that are not run efficiently. We have a state-run health program in Massachusetts that is running into higher than expected costs, and as a result is heavily in debt. I see other facets of health reform that are being totally ignored. None of these things give me much faith that my tax dollars will be spent wisely. I see a lot of knee-jerk reaction in our government and not a lot of thoughtful analysis of how to make a health care program actually work. When I see that kind of thought, when I see Congress saying "we're going to prioritize our spending and cut in these other places to provide the funding for a health care program", then I'll be much more inclined to support it.
Just my two cents.