Subsidiarity requires that needs be addressed at the lowest, most local possible level. But, the principle lives in conflict, in a manner, with solidarity, which demands that our concern lie with all people and the common good of all. Hence, while subsidiarity insists that matters are best handled by those closest to the people involved, solidarity insists that we keep a somewhat universal view and readily recognize the need to "escalate" matters. And health care could be argued from either end.
The need for some health care is universal. Whether that need is the same everywhere, I'm not sure. Nor do I know whether enough of the nations needs are similar enough to warrant mixing everything together in the same system -- there's no authoritative Catholic statement that I'm aware of from that perspective.
However, there's plenty to be said about the justness of the Affordable Care Act in other regards. The USCCB has issued multiple statements regarding the infringement on justice and moral freedom that the law as-is currently imposes. One, issued on 6/28/12 highlights (again) the lack of protection for those who wish not to contribute, on religious or moral grounds, to plans including abortion and contraceptive coverage.
There are a fair number of publications from the USCCB to the same regard: See here.
Generally speaking, the attitude of the USSCB has shown that it's not the "universal" nature of the act that Catholics should necessarily oppose, but the nature of it which prevents moral and religious opt-outs. The need for "universal" health care is pretty-well recognized by the USCCB; but the lack of respect for religious freedoms and the explicit inclusion of items which are "not healthcare" is a distinct and highly important problem.