If I think about time an American nowadays the first thing that comes into my mind is GPS. What WWVB or DCF77 (and JJY) was back then is now GPS timing capabilities. Much higher precision but of course a higher complexity for the receiver. [1]

I don't know about WWVB and JJY but the German DFC77 is not only AM modulated but FM too allowing for a better accuracy.

[1] https://www.hopf.com/dcf77-gps_en.php#chapter3