Did Constantine Directly Tell the Assemblies to Abandon the Yahudi Pasakh Custom?

Source: Eusebius, Life of Constantine 3.18–19 · 325 CE

What the ancient record says

Yes, the letter is not ambiguous: by abandoning their custom the assemblies could preserve what he considered the proper observance for future generations; the purpose was uniformity independent of Yahudi practice, a direct policy statement. Progression now visible: 2nd century (Asian assemblies keep the fourteenth day; Victor attempts to cut them off; others resist Victor), then 4th century (Nicaea addresses the observance; Constantine afterward advocates one common system, explicitly rejecting Yahudi practice).

Nicaea did not create the first Sunday observance, Sunday-based observance existed earlier; Nicaea/Constantine represent a major stage of standardization (a stronger, demonstrable claim). He emphasizes one common observance for everyone.

The conciliar letter likewise says those in the East who had formerly followed the Yahudi custom were henceforth to observe with Rome and the other assemblies (New Advent).