My cousins had an ink pen hanging by a string in their basement, as a visual lesson on pendulums. They swing all the way out to here, then you let go and they swing back and hit the basement wall with an empty thud. Pull back far enough and the pen will slam and then fall to the ground, since the string is tied to the cap. Behold: a pendulum. Back/forth/back/forth.
In much the same way, the US has been a primarily Christian nation, upholding many (but not all) of the values that we read in Scripture. In recent years, some people have seen the pendulum as being too far swung this way and not that.