Abortion is an issue where imposing one policy on the entire country is disastrous. There are passionately held positions at both ends of the spectrum, yet most of the population falls squarely in the middle. Imposing policy at the federal level generates polarization and acriminony that is desctructive of a civil society. Leaving abortion policy to the states allows for different outcomes in different places, which means a broad fraction of the population can feel its views have at least been heard.That's all fine, I guess, provided that you have no substantive moral or political views on abortion itself. Yes, the majority of the population "falls squarely in the middle" of the debate, but that majority consists of individuals, each of whom has his or her own preferred set of abortion laws. The catch is that it's unlikely that any of those individuals actually believes that abortion ought to have a different legal status in each state; it's much more likely they each think that each state ought to enact his or her preferred set of abortion laws.
This is a basic case of the fallacy of division. The mistake is thinking that because the collective opinion of the majority is muddled that the opinion of each individual member of the majority is similarly muddled.
It's not that there's nothing whatever to this compromise business, it's just that it's kind of a cop-out of the actual ethical question to just cut straight through to the compromise. There's no question that life is easier if you haven't got moral beliefs, or refuse to let them enter into the picture, so I can see the appeal of trying to abstract away from people's differing views. The fact, however, is that most people do have such moral beliefs and it's rarely productive or wise to act as if they don't or that they won't be important.