Jackson constantly changes characters, dialog, and events,
I can think of Arwen and the Flight to the Ford, Haldir at Helm's Deep, and Treebeard saying Tom Bombadill's line to Old Man Willow, but off the top of my head that's about it. To me, adding spectacle isn't divorcing from the core of the story just because it wasn't found in the books.
The Free Peoples of Middle Earth, in the movie, are not just being outgunned and outmanned by an enemy that is playing a long game...they're all pissed at each other over issues that weren't really issues in the books...and can barely band together at all.
As you mention, there were age-old mistrusts that many at the Council actively remembered. No one trusted Men. The Dwarves hated the Elves for Erebor, and the Elves hated the Dwarves for the closing of Moria, and further back for
technically being the first peoples.
And with the Council of Elrond, while much of the long-winded histories was cut out (and justly so; that would not translate well to a film at all) Boromir still selfishly vied for the Ring to be given to Gondor, and even looking to Aragorn with doubt. To which Frodo even gets annoyed. Gandalf speaks the Black Tongue, and Elrond even admonishes him for it. Gloin and Elrond even argue about the Three Rings, Boromir
almost mocks Bilbo, and no one could come to agreement with what to do with the Ring due to mistrust. The film simply shows the division that Sauron sowed in a much briefer span, but doesn't really add anything (besides temper) that was not already there. A "shouting argument" is unlike any of the characters and races
only because that wasn't proper in the 1940-50's. Had the time that LotR been written been different, they would most certainly be fighting beyond veiled insults and witty barbs.
While Boromir would eventually succumb to the desire for the Ring, it was obvious from his first appearance that he would, unlike in the books--how unlike a Man of Numenor, which he was.
No, right from the Council we see Boromir doubting Aragorn, not treating the Ring as the threat that it is, and blustering about the "strength of men" after Galadriel put the test to him.
Somehow, just in the nick of time, either Aragorn or Gandalf manages to convince Elrond's council, or King Theoden, or whomever to work together.
No, Frodo - in both the book and the film - settles the Council. I will grant you that the Beacons of Gondor replaced the Red Arrow, but consider that the Beacons require much less explanation. Théoden still needed convincing via the summons to muster to Gondor's aid.
I do grant you that the Rousing of Fangorn was far different in the books.
There are hints in the movie of romantic interest between Aragorn and Eowyn...and that somehow Arwen was willing to relinquish Aragorn and flee to the West, that she would accede to her father's preferences. An elf would not be so fickle, and neither would a Man of Numenor (also Aragorn). Yes, Eowyn fell for Aragorn, but it was not reciprocated.
In the films Aragorn - as in the books - respected Eowyn, but didn't reciprocate her affections. It is also written in Appendix A, V "The Tale of Aragorn and Arwen" that Elrond was quite upset about Arwen's choice, and basically told Aragorn that unless he was a King, Arwen would never marry him. In the films, she didn't really accept her father's choice, but was loyal to him as his daughter;
him sending her away brought her nothing but grief.
I grant you Sam; that was different than the book. As well as Faramir, though through the addition of letting Frodo go
after temptation of the ring, the film showed that Faramir was better in a way that would translate well to screen.
in the books, no one was ever close to the Nazgul for more than a few moments...but them magically hovering on their flying steeds, descending to the walls of Minas Tirith to grab people and drop them? Stupid, special-effects driven storytelling. Their main use in the books were their psychological oppression, which could have been easily created by having them scream, far above the city, and men blench and looking scared in response...
Which did happen. But if you've just got screaming from the clouds... How are viewers to know what is going on?
To me the bigger difference was the Hobbit movies than Lord of the Rings. The Hobbit was a children's story. Trying to turn it into a serious, high stakes epic high fanasy is like trying to do the same with My Little Pony.
From my understanding, much of the Hobbit trilogy was brought in also from "A Quest for Erebor" (which was basically The Hobbit from Gandalf's perspective, bringing the children's tale - in which the Ring wasn't even the One Ring - up to the more adult theme of LotR) as well as events explained and laid out in the Appendixes of the LotR books, like Sauron's occupation of Dol Goldur.