It's not a particularly titillating scene, but one that gives insight into the characters and what they're preoccupied with in The Americans' second season premiere.
The scene occurs from the daughter Paige's point of view, continuing with her growing suspicion that her parents aren't as normal/boring as she thought they were. She's also wrestling with unresolved issues from her parents separating and then taking a "long trip" at the end of last season. This might be why she opens that bedroom door and discovers something that we're all in denial about - that our parents are sexual too.
Vulture's write up includes some interesting stuff about how rarely we see untelegenic sex scenes like the 69 position on TV, and what showing such a scene says about the Jenningses reconstituted marriage. It's nice to see this show continue to feature such progressive and resonant moments amid all the violence and spycraft.