Someone—perhaps one of you will remember who it was—famously made the remark at Vatican II, when collegiality was being discussed, that holy writ only mentions one example of collegial decision making, when it records of the apostles: 'and they all ran away'.
One Cardinal Ratzinger first raised doubts about the theological underpinning of the priniciple in The Ratzinger Report, an interview with a journalist, Victor Messori, in the 1980s.
Looking at the way bishops govern their dioceses these days, one has a certain sympathy for his point of view. The point is, surely, that a bishop does belong to a college, but it is not primarily that of his brother bishops, but of his brother priests; those who belong to his diocese. It is them 'with whom he shares his priestly ministry', as the ordination rite puts it; it is to the care of this college that the people of the diocese are entrusted.
To jointly govern a country, rather than a diocese, risks all sorts of things; for instance (and not least) neglecting the very important Catholic principle of subsidiarity; it creates a system where one size fits all and, most crucially, it takes the bishop away from, precisely, the forum that he has been ordained/consecrated to serve.
A bishop's secretary of my acquaintance used to lament the huge sheaves of paperwork his master was expected to digest before every bishops' meeting. Paper generated by a new expensive civil service whose job it is to provide this stuff to justify their salaries. A priest friend observed that his diocese was employing (at full salaries) all sorts of people doing very little, but who had to nag or bombard already over-pressed parish clergy with paperwork, or demands for this or that, simply to have something to do.
Somehow, I think we need a simplification. Of course it is a good thing for bishops to meet, but it shouldn't be the principal legislative unit of the Church in this country.
As the Holy Father said all those years ago; bishops are of divine institution. Bishops' Conferences are not.