Michael is right: modern-day America is not a theocracy, and should not be. We are not to enact the same *judicial* code as ancient Israel and stone people to death for adultery, but we are to govern our individual and corporate lives by the same *moral* code. That's why the Mosaic Code was preserved for us in the Scriptures: to teach us God's perspective on our sins.
So clearly, He takes adultery very seriously, and as a result, we should view it with the same disgust -- rather than romanticizing and excusing it. (Bridges of Madison County, Terms of Endearment, et al.)