It seems to me that the American political system is simply broken. Canada could reduce the size of government and keep health care spending in check because in a parliamentary system with strong party loyalty, individual politicans are given 'cover' by their parties and are not held personally responsible for the taxes and benefits of their constituents. If the party in power makes a decision to cut benefits which will harm an individual politician's district, that politician isn't necessarily on the hook for it. The voters know that he has to vote the party line even if he disagrees with the legislation. He gets re-elected so long as the public feels his party in general is better than the opposition.
In the U.S. system, where every vote is a free vote, each member of Congress has to answer for his/her votes, and this drives NIMBY-ism and ever-increasing benefits without the tax hikes to pay for them, and it also causes wheeling and dealing which ultimately makes large regulatory packages like health care reform incoherent and bloated with pork.
I think American government works well when it's strictly limited. When Americans try to implement Euro-style social democracy, they fail due to the nature of American government. It is uniquely unsuited to centralized technocratic governance.
That's from Dan H. and he has more to say at the link.