Common Sense Media reviews, like this one. [1]

IIRC, there's a bit of sex in The Americans, and a fair bit of discussion of how the spies had to sleep with targets as part of their training, and in the field. The father character also has a pretty dicey relationship with a much younger woman/girl, in order to access her father's home office.

1: https://www.commonsensemedia.org/tv-reviews/the-americans

I don't know how accurate it is, but IMDb [1] will usually tell you exact episodes of inappropriate content. Individual episodes also have a parental guide, but it looks less used.

[1] https://www.imdb.com/title/tt2149175/parentalguide

I'd worry more about a particular scene of sexual violence in Season 3, Episode 2 ("Baggage") than any graphic sex scenes. It's basic cable, so you'll see some butt cheeks here and there but never any nipples. Watch S3E2 yourself in advance and then fast forward through the relevant part for your 13 year old. You'll know it when you see it.