I will admit that "you can barely buy a sedan in the US anymore" was a bit of hyperbole, but certainly they have declined precipitously, from 80% of the US new vehicle market 40 years ago to about 25% today [0]. You can still buy sedans in the US, but not from american car companies [1].

[0] https://mercercapital.com/insights/blogs/auto-dealer-valuati...

[1] https://carbuzz.com/eulogy-for-the-chevrolet-malibu-and-seda...