There is a strong sentiment in the US against the federal government overreaching its power. The
US Constitution explicitly states what powers the federal government has and what powers the states have. (The original Constitution consisted of the main article, plus the first ten amendments, which are collectively referred to as the Bill of Rights.)
One of the things that is explicitly defined as a federal power is the power to form a military. There are other vaguely worded clauses that some people interpret very conservatively and others interpret very liberally, as well as everywhere in between. For example, the Constitution states that the federal government is to "provide for the … general welfare of the United States". Liberals believe that providing healthcare can be reasonably seen as providing for the general welfare. Conservatives seem to believe that general welfare doesn't comprise much beyond the prevention of dissolution. In general, liberals see the Constitution as a "living document" that must fit with the times, while conservatives see it as set in stone and uninterpretable, meaning nothing more than what it denotatively says.
How much is it going to cost to pay for all this anyway?
For the federal government, predictions are that it will reduce the deficit. For those that don't currently have health insurance, it will cost them a payment they're not making already. I imagine that the majority of those people don't have health insurance because they can't afford it, and will likely be subsidized. The people who get "screwed" are those that can afford health care, but choose not to have it anyway. My opinion is that those people are being selfish. Few people can afford to pay outright for cancer treatment, so those people are willing to chance that they won't get cancer against someone else picking up the tab. (Cancer being a standin for any expensive illness.) There are also increased taxes on the wealthy (those that make over $200,000 a year individually or $250,000 as a family) to pay for the subsidies given to the poor. (Also, people don't like redistribution of wealth, unless it's to generate a greater income disparity. "You're taking my hard-earned money to give it to some lazy slob!")
The estimated total "cost" of the bill in higher taxes and repurposing of Medicare funds is just under one trillion dollars over ten years, but that doesn't include any cost reduction estimates. A Nimitz-class aircraft carrier is about $4.5 billion.