The Protestant Episcopal Church in the United States of America, otherwise known as The Episcopal Church (which name is hereby recognized as also designating the Church), is a constituent member of the Anglican Communion, a Fellowship within the One, Holy, Catholic, and Apostolic Church, of those duly constituted Dioceses, Provinces, and regional Churches in communion with the See of Canterbury, upholding and propagating the historic Faith and Order as set forth in the Book of Common Prayer. This Constitution, adopted in General Convention in Philadelphia in October, 1789, as amended in subsequent General Conventions, sets forth the basic Articles for the government of the Church, and of its overseas missionary jurisdictions.
Now, the way I read that, the ECUSA defines itself as being a member of those churches in communion with the See of Canterbury. If the See of Canterbury says, "Do 'x' or you are out of communion", you do it or you're out.
True, but being in communion with the See of Canterbury might not be the same thing as being in communion with the world-wide Anglican Communion.