I'm not a Catholic either; nor am I an Alexander Hislop or Jack T. Chick style Catholic basher.
Pope Francis needs to learn from history, Part 1. The League of Nations and the UN were and are abject and monstrous failures. Not because they were/are too weak or too small, but because the price of getting something close to all nations' participation is giving up the moral standards by which a Stalin or a Hitler or a Mao or a Castro ... or a Saddam or the Iranian Mullah-cracy or Sudan or ... can be condemned. Accepting monsters as members entail accepting their monstrosity ... and even letting monsters sit in judgment of decent nations.
Pope Francis needs to learn from history, Part 2. Giving credit where credit is due, the Church of Rome (as distinct from the Greek Church of the Byzantine Empire) was the unifying social force that rose above the rubble of the Roman Empire, preserved much of Greek and Roman thought and civilization, mitigated the violence and chaos of the Middle Ages, and pointed to a path back to civilization. The Renaissance and "Enlightenment" did not arise ex nihilo.
That said, the socio-political power that the Catholic (Roman) Church brought arrogance, corruption, and decadence. Even a Catholic source such as the Catholic Encyclopedia doesn't try to mitigate events such as the comedy of horror often called the "Corpse Synod"; nor does it pretend that Pope Leo X was a great spiritual leader. Those are but two examples.
The lesson Pope Francis needs to learn from history, including that of his own church, is that world government cannot but devolve into a horror, because the humans it would govern do the governing. The sinful human beings who would be governed would be governed by sinful human beings.
In terms of the US Constitution, "Separation of Powers" was incorporated so that, in the extreme, there would be chances for decent people in one branch to bring a halt to corrupt persons in another branch. Efficiency was intentionally sacrificed to put in place checks against human sin.
