I loved The Americans, and have been thinking about doing a complete rewatch soon. But it is a very different show from Homeland. The showrunners slow it down and really do their own thing in the latter seasons once they knew they didn't have to get ratings and FX gave them the blessing to wind it down on their own terms. At times it was a pretty tough watch because there isn't a lot of levity or light/humor relief, but it was a show that would stay on your mind for days after.
The marriage is the central theme of the show, not the spycraft. I think this show and Friday Night Lights have done some of the best jobs at showcasing a marriage in television, but they do it in completely opposite ways.