Throughout its distinguished history “The Americans” has succeeded in projecting a strange and powerful sense of timeliness, no small accomplishment for a work set in the 1980s Cold War era and packed to its rafters with period detail. You knew the kind of writerly enterprise that was at work here when the plot line led, one season, to a captivating look back at EST, the self-development obsession of the era, with depictions of its meetings, its faithful believers, or those searching for reasons to believe, all worked smoothly into a saga about undercover Soviet spies.

Season...