Sometimes a miscarriage requires a procedure that is considered an abortion, nobody wants that to be illegal.
Huh? While the technical method may be the same, it is in no way considered an abortion and no state is (or would) try to forbid it.
We also don't want a debate between a rov who says halachicly the doctor should terminate vs the secular law that says its a crime.
This is a more likely scenario, and we should certainly advocate for laws that allow such abortions.
The issue will be that any law that allows for abortions in the case of threat to the health of the mother will inevitably be abused by doctors who think all abortion should be allowed (kind of like medical marijuana laws were).
This is going to cause states to clearly define what is considered a threat to the life of a mother and presumably in a way that conflicts with halacha.