Over at Thinking Anglicans, someone has opined that the departure of individual dioceses from The Episcopal Church is analogous to the departure of the Church of England and the See of Utrecht from the Roman Catholic Church.
These are not properly analogous, however, and not simply as matters of scale. The diocese -- all claims to the contrary notwithstanding -- is not self-sufficient in the Catholic tradition, in part because it can only obtain a bishop with the consent of the bishops of other dioceses of the province of which it forms a part (or, in some places, the metropolitan or archbishop). If it is a "unit" is like a cell of a body, or brick of a building: not self-sufficient on its own.
The historic actions in the 16th and 19th centuries, whereby the Church of England and the See of Utrecht severed their ties with Rome relate both to their original autonomy and to the understanding that these bodies represent "churches" rather than simply dioceses. (This is what having an archbishop is about, in part, and having metropolitical or provincial status.) The "national church" or province was the minimal defining entity as a "church" in the Christian (i.e., Orthodox) tradition until Rome began to assert a universal primacy. Individual dioceses have no authority to withdraw from their province unilaterally; national churches do have the right to assert their autonomy from the central hegemony of Rome. Two different things.
Tobias Stanislas Haller BSG