What's excellent, even superb, about the show is the way we care about the two murderous KGB agents, Elizabeth and Phillip. This is testament both to the fine acting of Keri Russell and Matthew Rhys, and the convincing story lines they're playing out - convincing because we can believe that a married couple with two children, seemingly leading a conventional suburban life in the early 1980s, are in fact infiltrating the highest offices of our government - including the home of Secretary of Defense Caspar Weinberger - and ready to kill in a heartbeat when necessary to save themselves and sometimes the mission. Their marital problems similarly ring true, even when juxtaposed with their expertise in the martial arts.
Also superb is their boss Claudia, played by Margo Martindale. She always gives a powerful performance, but her mixture of toughness and compassion, of loyalty to the KGB but also her own people, is one of the most appealing parts of the show.
The one point that I still can't buy, and which got even worse in the finale, is the idea that Stan, an FBI agent whose very beat is hunting KGB agents in America, just happens to live next door. Early on in the series he was indeed suspicious of Elizabeth and Phillip, but they convinced him otherwise in an impressive series of moves, and he apparently has been a believer ever since that the two are the nice, normal couple living next door that they are pretending to be - in fact, believes it even when Elizabeth and Phillip take a little "pause" as a couple, but continue their joint KGB missions.
In the finale, this is ratcheted up yet one step further: Stan has sketches of the KGB couple - sketches of Elizabeth and Stan in good disguise - but, still, he doesn't register a flicker of recognition, any sense that something looks familiar, when he sees Elizabeth in flesh, still under disguise.
An editor once told me that readers will allow one thing that doesn't ring true in a story, but that's it. Whether the Stan story is just one thing, over and over again, or more than one, I can't say. But I do think it is a drag on another otherwise outstanding new series, which I'm looking forward to seeing more of next year.
See also The Americans: True and Deep ... The Americans 1.4: Preventing World War III ... The Americans 1.11: Elizabeth's Evolution