Obamacare: Who Hates You, Baby?
Start with the Tea Party ideological anti-redistributionist nuts. In the end, that's a pretty small crowd, electorally speaking - perhaps 20 % or so. Add in a few extreme leftists, who see it (correctly) as a deal with the insurance company devil. Many of my contemporary elderly, who believe, somewhat delusionally, that it cuts Medicare. Small businessmen, who really really don't want to have to pay for insurance for their workers.
These last are probably most important, because they both understand the issue and have a lot of clout in the communities. What they probably don't understand - yet - is how much the government shutown and seemingly increasingly probable government default is going to cost them.
Of course single payer, not tied to employment, would have fixed many of these problems, but given the combined power of the medical-insurance-pharmacy complex and the ideologues, that was never going to happen.
If Obamacare and the US economy survive the current convulsions, the work-health insurance link could be undone in some future adjustment.