Muslims are such a small minority (less than 1 percent in the US) that they have no political power.The specifics of what's in Sharia law are irrelevant. It doesn't matter whether Sharia is the most oppressive medieval framework for a nightmarish theocracy. In the United States of America, only U.S. law governs. Period. Supreme law of the land" nails it down pretty well. I don't see anything in the constitution about exceptions made for religious law, and their is no law that supersede the U.S. Constitution.
Sharia is deemed by Islam to be "revealed," in that it was supposedly handed down by Allah himself, and as such is perfect, unchangeable, uninterpretable, and beyond the reach of man to alter it. In other words, Sharia is undemocratic.