When I heard Keri Russell would be playing a fierce KGB agent in FX’s “The Americans,” I had the same reaction I had when I heard Claire Danes would be a bipolar FBI agent in “Homeland”: It won’t work. Both actresses broke through in youth melodramas on TV, Russell in “Felicity” and Danes in “My So-Called Life,” and neither seemed to have the dark notes needed to be convincing as aggressive nationalists. They struck me as fine romantic-drama leads, but too thin as performers to evoke global consciousness and the gonzo commitment to do absolutely anything, even sexually, for their country.

In both cases, I was dead wrong. Danes has given the performance of a lifetime in “Homeland,” and Russell is remarkable in the first-rate “The Americans,” in which she and Matthew Rhys play fictional sleeper KGB agents Elizabeth and Philip Jennings in 1981. She brings out both Elizabeth’s backbone and her dizzying spiral of identity issues. Russell effectively makes Elizabeth into a ruthless zealot, an old-world moralist, and a fretful mother to the two children she and Philip had after relocating from Russia to the States. If you look just behind her suburban-mom eyes, you can sense her unwavering contempt for America and its freedoms.