The "traditional American family" is a myth.
Well I'm sure some families exist that match what those who trump the concept have in mind. But it is indeed a myth that it was ever dominant in our society. It was once much more common on paper than it is now, but the underlying realities very often didn't match the idealistic stereotype. Many women were stuck with alcoholic dead-beat husbands, or were viewed as unmarriageable if they left them, because divorce was frowned upon -- and children were stuck in the miserable home. And most people didn't marry for love, they married out of economic necessity and lack of any other available marriage partners in their area, or due to the woman being pregnant. Now that there are lots of other options for how to arrange one's personal life, I suspect a much higher percentage of traditional-on-paper families are actually happy, functional family units, than in the past (there are just a lot fewer of them).