A lot of critics say that “The Americans” on FX (Wednesdays at 10 p.m.) is one of the best shows on TV. We hear that sort of determination a lot, but in this case, it’s absolutely true. If Reagan-era, Cold-War spycraft seems a juicy setting around which to set a series, you must tune in. (Back episodes are available on various streaming services. Catch up!) In “The Americans,” Keri Russell and Matthew Rhys star as two KGB spies posing as a married American couple who run a travel agency in suburban Washington, D.C. Their cover is flawless; their defenses are deadly; their disguises thorough and varied. In crafting their cover, they produce two children, and their eldest recently has learned what her parents REALLY do for a living. Now they have to convert her to the cause. And maintain their cover and their various identities. And safeguard a bioweapon. Stylish shooting, intriguing dialogue (every line seems to have double meaning), and brilliant acting amount to Wednesday-night appointment TV.