But from what I remember, as I do not have the book with me, it is that according to what recounted in one of the volumes of his work and interpreted it was crucial for future England OTL is that there was a council or great Synod of the Church British leaders attended by representatives Anglo-Saxons and Britons, Saxons, Irish and from Rome.
I think you're talking of the Synod of Whitsby.
I agree entierly with you that it wasn't a non-event, if badly known (Bede is the more close source with Eddius, wirting several decades after the council, and it's dramatically absent from both AS and pontifical archives).
From what I have at hand myself, most of the differences at hand were quite minor and already on the path being resolved : an english-speaking historian apparently called the whole thing "a triumphant push against an open door", as Ionan traditions were challenged even in Ireland : Oswy, in order to replace Ionan clerics, used other Irish ones, not continental or Romans after all. (Bede mention an irish monk called Ronan, having studied in Gaul and Italy the continental uses, convincing many even before the synod.
Now Bede is more than harsh on Finan, so it's to be taken with a grain of salt)
On this part, the trend was by the VIIth century already going against Irish traditions (as it went against Aquitain or other regional computs as well, which had a less important historical posterity, mostly for ideological reasons).
Now, the historiographical point is less about some really minor points, than structure and organisation : basically about who would get to have the upper hand on ecclesiastical lead.
Ionan and Irish churches were more centered on monachial and abbatial structures (while episcopalian weren't absent, but secondary); while others (and specifically in southern Britain, trough continental influence) put the stress on bishops.
It's especially interesting in relation with their link with kingship, as in virtually all the continental kingdoms, you had a situation that evolved from Late Roman's : the king (inheriting imperium) more or less presiding over an episcopal assembly (of course it evolved from this : Councils of Toledo points how, but it didn't diverged radically at this point).
Having the king presiding over such synod, and getting to make the decision, was already (IMO) pointing how Ionian's positions didn't exactly began as the winning side (while Augustine had to battle with Britto-Romans waiting for a general assembly).
It's possible that Oswy's son, that expelled some monks out of Deira (that he ruled) was lead by some similar...not exactly political, but say ideological conceptions on who had a say on religious matters.
As well, I think it's interesting to point that queen Eanfeld was Kentish and a kentish priest at her side, with the aformentioned huge Frankish influence over the southern kingdom.
You likely had a struggle of...not exactly influences (while Ebroïn, majordomo of Neustria, seems to have took an interest on the question, in addition of Agilbert's presence) as it wasn't about interventionism, but close enough (I don't have the right word in english in mind, sorry).
For what matter the situation at hand, "Romans" (that had to be understood, IMO, in the most larger sense) were already present and influential, not only on southern Britain, but as well in this "encounter point" that was Northumbria, then at its apogee.
While not a world-shattering event (it had virtually zero consequences on the continent), I agree it was important for English history.
But less as a tip on the balance, than part of a wider process : after all, Bede points that most of the organisation left by Colman remained in place for years after his departure, and most of native liturgic and religious structures remained in place up to Norman conquest and well after (Davidian revolution, conquest of Wales, etc.)
Calling Whitbey "crucial" is, IMO, too much : it was important for the era, get for diverse reasons an historiographical importance (a bit like Battle of Tours was important, just that it get blown up out of proportions historiographically), but eventually even without it, Ionan decline would still have been a thing.
The Armenian Genocide articles aren't, for once, bad. Quite good actually, if you want to take a look.
https://en.wikipedia.org/wiki/Celtic_Christianity
https://en.wikipedia.org/wiki/Synod_of_Whitby