She mentioned somewhere that she sees India and Japan as good case studies in how modernist polytheistic societies works.
Not exact models of what a modernist Rome would look like, though. For one thing the Roman legal system, in its various forms, was a different creature. They had slavery ... but also very liberal marriage and divorce laws compared to most societies in history.
They're also one of only two legal systems which developed torts -- in Roman law, delicts. As an innovation torts/delicts take a lot of pressure off the state to provide regulation of commercial and personal behaviour, because a lot of it is then handled at the lower level by individuals and companies.
A lot of the Roman impatience with early Christians was due to their energetic ... disagreements ... about your statement that "the trinity is nothing if not an expression of polytheism".
Right, however the Pauline creed places Jesus as divine alongside God. This is polytheistic as it has assigned divinity to something/someone other than God alone. And predates the period you describe. Of course, Christianity has become more and more polytheistic over time and now resembles, particularly in the third world where saint worship and veneration of bones is common practice, a belief system that is only marginally more monotheistic than Hinduism.
Nowadays, the only two major religions that one can say are even remotely monotheistic are Judaism and Islam. The Islamic notion of "tawheed" (unity of God) being a good example of a belief system that is genuinely monotheistic.
The actual question of whether Jesus is "alongside" God or whether he is God (and whether God is one being with three aspects or three independent aspects that combine like a divine Voltron) is literally the root of most of the nasty bustups of the first few centuries of Christianity. Those early bongpipe debate clubs really got out of hand.
In terms of veneration of saints etc; that's mostly because the early church deliberately went out of its way to absorb existing customs and beliefs. Many of the dates in the Christian calendar are pretty much stuff scribbled over the top of an existing pagan festival. Christmas pretty much replaces the Saturnalia, for instance.
>* This is polytheistic as it has assigned divinity to something/someone other than God alone.* //
It sounds like you're outside your comfort zone. Jesus is not other than God [the Father or God the Spirit] in orthodox [little-o] Christian belief. It's confusing for sure.
Catholicism includes the veneration of saints but they are categorically not gods, nor are relics gods, so how can the inclusion of such elements indicate polytheism.
Interesting that you mention Islam as one of the criticisms of Islam is that many supposed adherents appear to worship Mohammed as a god, certainly as much as Catholics "worship" the beatified. There is also the notion, warned against in the Quran IIRC, of worship of the djinn which could be considered analogous in some ways with veneration of the saints.
The orthodox belief you state that Jesus is the same as God is basically equivalent to the Hindu belief that their various gods are just different facets or aspects of God (with a capital G). If Christianity is monotheistic then, by this definition, so is Hinduism.
As for veneration of saints and relics, then anything that worshipped is a god and asking for blessings, intervention in worldly affairs, etc are all acts of worship. So when someone prays to a particular saint seeking something they are engaging a polytheistic act just as one who prays to an idol is engaging in polytheism.
I am not sure about Muslims worshipping Muhammad. Maybe in some polytheistic branches of Islam such as sufism and so forth which were themselves influenced by hindu/christian/etc ideas.
Some Hindu thought tends towards monotheism in considering the Brahman to be personal but that's certainly not true across the board. Personally I don't know enough hinduism, or hindus, to comment properly.
For those that don't consider the Brahman to be personal, and some that do, then within their philosophy [or practise] there are certainly distinct gods with distinct beings.
Not everything that is worshipped is a god. You can certainly worship something which is not divine - one of Jehovah's big beefs (!) with the early Hebrew tribes was their tendency to make things to worship.
When Catholics appeal to dead "Saints" (quite contradictory to NT use of saints to mean those who believe in Christ Jesus and so are saved) they ask for them to intercede before God for them. The thought is that the Saints are in heaven and so have the ear of God in a way that mortals do not - that is not deifying the Saints. It is not polytheism in practise or reality.
Not exact models of what a modernist Rome would look like, though. For one thing the Roman legal system, in its various forms, was a different creature. They had slavery ... but also very liberal marriage and divorce laws compared to most societies in history.
They're also one of only two legal systems which developed torts -- in Roman law, delicts. As an innovation torts/delicts take a lot of pressure off the state to provide regulation of commercial and personal behaviour, because a lot of it is then handled at the lower level by individuals and companies.