John Wesley never intended the Methodist movement to leave the Church of England, and he never accepted that bishop, priest and deacon named three distinct biblical orders rather than one order of presbyter exercising different functions. When the American Revolution cut the Methodist societies in the United States off from Anglican clergy and sacraments, Wesley acted outside his own authority as a priest of the Church of England and ordained Thomas Coke as general superintendent for America in September 1784, sending him with instructions to ordain Francis Asbury to the same office in turn.
Coke and Asbury, meeting at the Christmas Conference in Baltimore that December, promptly took the title bishop for themselves instead, over Wesley's written objection. Wesley considered the change a betrayal of his own theological position, since he held that superintendent named a function of oversight within a single ministerial order, while bishop implied a separate, higher order in historic succession, the very claim the Methodist movement had no basis to make and Wesley had spent decades denying the Church of England needed to make either. The dispute was never resolved to Wesley's satisfaction; the Methodist Episcopal Church kept the title bishop, and it has remained standard across the largest American Methodist bodies since.
Smaller bodies that split from the mainstream Methodist Episcopal Church on other grounds, chiefly holiness movement churches formed in the late nineteenth century, revived Wesley's original term instead, reading the adoption of bishop as one more sign of the institutional formality they were leaving behind. The naming choice a Methodist body makes for its chief officer, bishop or superintendent, still marks which side of that nineteenth century split it descends from.