It was one of the most dramatic episodes of the season. Monica Lewinsky, the heroine of “Impeachment: American Crime Story,” strikes an immunity deal with federal prosecutors, and President Bill Clinton admits to having had an affair to a grand jury and the nation as a whole. The episode also brought Hillary Clinton, portrayed by Edie Falco, to center stage for the first time.The only thing missing was a big viewing audience.“Impeachment: American Crime Story,” a series that attracted lots of media coverage before its September premiere, airs on the FX cable network Tuesdays at 10 p.m. Last week’s episode ranked 15th in the ratings for cable shows that day, tied with ESPN’s “Around the Horn” and MTV’s “Teen Mom.”Produced by Ryan Murphy, “American Crime Story” has a lot goi …
