The thing is, broad-church Anglicanism, whether English or not, is essentially Protestant--as Queen Elizabeth I rightly insisted. Like confessional Lutheranism and Calvinism, to be sure, it considers itself Catholic in the only sense that matters. In that sense of 'Catholic', Roman and Eastern Catholicism do not together constitute the Catholic Church, but are at most branches thereof, if not sects. But the belief that the communion of churches calling itself "the Catholic Church" is not, in fact, the Catholic Church is what makes Anglicanism in all its forms Protestant. Thus the terminus at which Leithart's "end of Protestantism" arrives is--well, Protestant.
It should be evident that all Protestant attempts to transcend the thing that used to be called Protestantism--such as "non-denominational" Christianity, or pentecostalism--end by coming similarly full circle. That is inevitable so long as those making the attempt fail to see that the Church Christ founded perdures as a visible and unitary whole, from which all other self-described "churches" are in varying degrees of schism--even as those degrees mark, inversely, the degrees of "imperfect communion" with the Church Christ founded.