I think that's quite speculative to be honest : we don't know anything about Romance speeches in Mauretania, or even if they really emerged to begin with.
Now, without having much to support it, I'd rather think that if Romance speech was to root itself in coastal Mauretania, it'd be closer to Hispano-Romance speeches giving the social-cultural proximity with Betica.
Agreed, that would probably be the case, but perhaps there would be more similarities between the Romance of Tingis and Carthage than between certain regions of Iberia like Cantabria and Galicia.
While there is a known proximity with Sardinian phonology, and maybe Hispano-Romance phonology, I didn't saw Italo-Romance being mentioned.I was under the impression that the thin knowledge we have about it would make Afro-Romance more of a south/western Romance language, but I might miss something there : what does make you think about a possible connection to Italo-Romance?
IIRC Sicily had many contacts with North Africa, and immigrants from North Africa arrived there in Late Antiquity. Combined with their shared Phoenician heritage, and the similar history to Sardinia, as well as shared traits of Sicilian with Sardinian, Sicilian seems to have some influences or otherwise shared some traits with African Romance.
They were certainly more present, (Both neo-Punic and Berber) in African provincial culture than their counterpart in western Romania (Gaulish influence is not even superficial, and Germanic influence is mostly phonologic and vocabulary based in Gallo-Romance for instance). I'd expect Berber, in the case of a Berbero-Roman ensemble pulling a Merovingian in the VIth, to at least play the role of Germanic speeches in Gallo-Romance, with the distinction having another important language being spoken already in the region (and likely survived as Afro-Romance until the XIth to XIIth centuries). Now I agree that Neo-Punic might disappear earlier ITTL due to being itself importantly Berberized in Late Antiquity, but that would reinforce Berber influence IMO.
The Berber hinterland was huge, and in places like modern Morocco south of Roman rule, dominant. Seems like the Berber language area would be progressively eroded over the centuries as it was under Arab domination, although in much of modern Morocco, perhaps not at all (it all depends on economic and social conditions, really). Still would be interesting if the local Romance language ends up with many words starting with a-/ta- (Berber masculine/feminine) as a result of Berber influence.
There's no much vulgar Latin written sources tough : Merovingian Latin (as a form of Late Latin) for instance is more a decomposition of classical Latin rules than representative of the evolution of common speach (for exemple, Merovingian Latin uses variant of classical cases essentially as a decorative tool, while Vulgar Latin does reduce and systematise them).
Most of what we know of Vulgar Latin forms comes from partial epigraphy since the beggining of the millenium, sources written in classical Latin, some features of Late Latin and reconstruction from early distinguished romance languages (such as in the Oaths of Strasbourg).
What we know of Vulgar Latin at this point doesn't really help highlight the regional differenciations, because all speeches went trough the same development altough with various result depending of ad/sub-strates and contingential events. If you're interested this site provides with a lot of information.
I'm just basing things off the epigraphy, records where we can tell the speaker is using what they know of Latin (letter writers not using templates, there's one I've seen from Africa where the writer lapses into "Punicisms"), etc. I'd be curious of how the regional Latins were differentiating. Gallic Latin vs. Iberian Latin vs. African Latin and such.
Now, you're right that we can deduce something of African Late Latin trough Spanish sources, for exemple.
I don't agree with the author that Africano-Romance had such a marking influence into the making of Ibero-Romance phonology, but African Latin certainly did had an enormous prestige in Spain, as well as an Afro-Romance adstratum. Still, the comparison with Sardinian might be more fructuous at this point.
Eventually, for what matter Afro-Romance, we even have less exemples than usual, due to scaracity of aformentioned sources, a more important connection to late classical Latinity, etc. and the more important survivance of non-Romance speeches in Africa (and their possible substratic or adstratic influence on Africano-Romance) make it a bit distinct there.
That's an interesting paper to say the least. But wouldn't a lot of those supposed African Romance traits be more reflective on "Mauretanian Romance" as opposed to the African Romance of Proconsular Africa and Carthage (although some features noted there like /v/ and /b/ merging are noted all over Africa). And given how little we know of both African Romance and early Iberian Romance, it begs the question as to the nature of Vulgar Latin spoken in places like Baetica, the Balearics, and elsewhere in southern and southeastern Spain.
I have read that if we butterfly Islam then a strong North African romance language is pretty inevitable outside some black swan events to strengthen Berber.
It isn't just butterflying Islam, but also the events that come afterwards. A strong African Romance along the coast and in most of modern Tunisia/Tripolitania, probably, but a strong African Romance in the Atlas and such? That will depend on social conditions and the economic policies of the states which rule the region in the centuries after.
I do really think that after Islamic sustained conquest, the long term survival of African Romance is very unlikely--even Coptic hardly survived as all, and only liturgically. But I don't think that the entrance of Islam doesn't guarantee conquest of North Africa. The invasion can go poorly, or the nomadic people can reject Islam or eject the conqueror, or the conquest can be spread thinly, being so far from the Arab power base, that the Islamic veneer is shaken off in a time of political turmoil and never restored. The conquest of Egypt could've gone a lot worse, or the Arab conquests in the East could've been more fruitful into India--there are a lot of factors that could direct Arab attention elsewhere. Africa is the low hanging fruit, but there just as many other opportunities closer to home for the Arabs.
I disagree. There's attested records of Vulgar Latin in Africa well after the Islamic conquest, and Latin-speaking Christians are often mentioned in that period. The Pope was occasionally adjudicating disputes in that community into the 11th century, where we know there were several active bishops.
It's more surprising that indigenous Christians in the Maghreb went entirely extinct, whereas in many other places in the Middle East they survived. It seems that in addition to the usual erosion of the Christian community in the Middle East, the Banu Hilal, Almohads, and others in the early 2nd millennium probably finished them off for good. But it's easy to see with different events in that region, the indigenous Christians would survive, albeit being Arabised linguistically (like many Middle Eastern Christians), but we'd end up with a lot better records for African Romance (which might go extinct a few centuries later than OTL).