Save for papal states, it pretty much defined Christendom. Indeed, there were times in which potentates would not rush to the defense called for by the Pope, himself. They would weigh their options. Ultimately, the modern notion of separation of church/state doesn't so much wish to deprive the court of its bishops, but the laws of their Catholicism. The King was still the King, when Kings mattered, and much to the dismay of all of Heaven during the reign of Henry VIIIth and his 'Catholic' archbishop at Canterbury. But the moral law, before, and elsewhere, even for pretender Kings even in England, was judged against the Catholic standard. It wasn't papal control of foreign lands that made it Christendom. It was their voluntary confession of the higher law and basis for jurisprudence that made it so. That small confession of the same, however intentionally made vague, was part of the founding of the US. And the US has prospered, not always for embracing the Faith or for dealing fairly in business or great social projects (the robber barons, and such). But the social compact is still one based on a confession of the higher, if not now that of Catholicism, itself. It's the remaining moral hope for this nation, and perhaps one explanation for why this remains a nation with the largest number of at least self-professed Christians. Contrast with the French who denied this altogether in their insurrection, and created The Terror and Bonaparte, and a legacy of shame, defeat, and a slew of new 'republics'.
Please see my post #104 that illustrates the Catholic view on the church and state relationship prevalent since Gregory VII.
"Separation of church and state" has a precise meaning these days, thanks to secular theorists of the French Revolution, Marxist-Leninists, and some utterances of American Founding Fathers that never made it into our constitution. It has become the pathetic reality for us in the US thanks to the secularist fanatics in government. When a Christian monument is vandalized by court decree because it is on public property, or a politician dismissed because he considers his actions God-inspired, that is separation of church and state. Catholicism never stood for this and never will.
The US Constitution rightly forbids the US government to establish a church. It does not say anything about a church directing the government. This may not be identical to Gregory VII ideal, but it is compatible with it. Note that after absolving Henry IV the Pope turned him over to the electorate of the day, -- the Augsburg council, -- just like the church today should extend or withdraw its blessing from civil government, while leaving the choice of civil leadership to the political process.