Did a Leader in Rome Actually Try to Cut off Entire Assemblies Over the Pasakh Date?

Roman leader: Victor · Asian leader: Polycrates · late 2nd c. · Witness: Eusebius, Ecclesiastical History 5.24

What the ancient record says

Yes. Eusebius says Victor, who led the assembly at Rome, attempted to cut off the assemblies of Asia and neighboring provinces from common unity because they maintained the fourteenth-day practice, their refusal became serious enough that Rome attempted to exclude them: a struggle over conformity.

No emperor enforced Victor's decision (still the 2nd century), Victor had ecclesiastical influence, not Constantine's later imperial machinery; this shows pressure toward uniformity before imperial Christianity. Eusebius says Victor tried to declare the brethren of Asia and neighboring provinces completely cut off, issuing letters announcing their exclusion, stronger than mere disagreement: attempted institutional separation.

Polycrates's letter shows resistance.