Whenever there is a shift in basic ideas, someone always asks a question like this. There's no such thing as a "moral cliff." Humans make their own standards, and when those standards change, we change with them. Simple as that. Of course, change is painful for people, and some who liked it the way it was will yell and scream about how we are going down hill. This is the same argument we've had since our time began. I bet that you could ask any generation and they would talk about how moral they were and how immoral kids now a days are.
America is not headed off of a moral cliff. There are many moral people still living in this country. Of course there are a lot of immoral people, but it has always been that way. I think people need to focus on the good things and moral people instead of the bad.
Its hard to actually have a clear definition of what morals are. Any culture or social structure will look at morals differently and we have to take into account what they are. Americas morals seem to be shifting but the basic human decency still is out there, but just because we are becoming more liberal does not means its going away.
To claim that any one group or time period has a monopoly on morality is naive. Over time moral compasses shift and lead us in a new direction. So long as the basic tenets of human morality are held constant, for example don't kill or steal or other basic laws required to keep the peace, society will be fine. Just because we are becoming more liberal and accepting as a society does not mean we are throwing our morals out the door.