Some of you seriously need to do some research. I need a brushup and am not done researching this out, but it's a bit disconcerting to see the level of (apparent) naivity out there.
Superior healthcare? I'm really not sure what you're using as your measuring stick, but in terms of the 5-year cancer survival rates, no, these countries have vastly inferior healthcare systems when compared to the US. Let's just take colorectal cancer. Five years down the road, 60% of US patients are alive and kicking. In the UK? How about 36%? Yes, you read that right. Check it out.
http://news.bbc.co.uk/1/hi/health/272078.stm
Just from a simple economic perspective, allowing money to circulate through the system is a smart move. The more money changes hands, the more likely an economy is to grow. Paying money out in taxes, on the other hand, is not a formula for increasing productivity or stimulating economic growth. People need to feel as if they are in control of their money. It breeds optimism. It increases entrepreneurship, and it increases overall wealth. In the end, more economic growth equals more tax dollars. (this is way too simplified, I know, but how else are you going to try to summarize?)
But to move away from the more theoretical, national healthcare causes a lot of problems. In the UK, waiting lists are so long that patients in need of transplants, for instance, are now being backed up to the point where they will be in critical condition before they receive a transplant. Doctors are leaving the national system because they are over-worked and undercompensated and can make more money in private practice. Getting people to commit to medicine is becoming more difficult.
IMHO, the biggest problem facing American healthcare today is the growing number of illegal immigrants and our decreasing birthrates. People, if you haven't figured it out, those who can pay for healthcare in our country and those who have insurance aren't reproducing. At the same time, illegal immigrants are pouring across our borders and essentially showing up in the ER and taking healthcare for free while racking up tremendous bills. They pay very little in taxes and expend exhorbitant sums of money this way. I heard on the radio that 11 of the 30 hospitals in the San Fernando Valley had to shut down due to financial losses while the population of the area was sky-rocketing. And you people say just offer healthcare to everyone? That will fix things? Are you trying to put us 6 feet under? Just FYI, there are more illegal residents in our country than there are people in Georgia (our ninth most populous state) and Montana combined.
Another problem that comes with relying on a national healthcare plan is that it requires such a huge commitment and a steady tax base. Right now birthrates in this country are declining. The nations of Europe, if they do not amend their ways, will face economic collapse and a healthcare disaster in a few decades. The birthrates in Spain and Italy? Less than 1.20 children per mother. In former East Germany, rates are as low as .83 children per mother. Replacement rates are 2.10 children/mother. In the US, we're down to 2.07. You see what I'm saying? In a few decades, the average European is going to be 53 years old. Price of healthcare changes in which direction as we age?
http://news.bbc.co.uk/1/hi/world/734123.stm
Declining birthrates are due to a number of reasons. The increased number of households living on two incomes, increasing levels of hedonistic behavior (having a family wasn't seen as a sacrifice 50 years ago), the decline in religious observance, and also to a general weakening of the concept of family.
On the problems in Canada:
http://www.csmonitor.com/2002/0228/p07s02-woam.htm
On decline and aging of world population:
http://www.kstatecollegian.com/issues/v104/fa/n039/opinion/opn.roney.friday.html
More problems in the UK. Have cancer? Wait 10 months and we'll start to treat you.
http://news.bbc.co.uk/1/hi/health/675968.stm