So you might end up with an area of Celtic cultural dominance roughy equivalent to OTL's Rome? It's unlikely that any one power would be able to unite these areas seeing as they have roughly equivalent technologies and statecraft and the whole Euro-Med region would be divided into Celtic-dominated states, heavily influenced by the Greeks. Combining Celtic weaponry, tactics and ferocity with Greek discipline... Awesome thought.
Hellenistic culture would still remain strong in the eastern Mediterranean even if they were conquered by Celtic mercenary armies. I should probably exclude the Seleucid Syrians from this fate, unless their empire somehow breaksdown or the Parthians succeed despite the removal of Rome from the picture. But I can certainly see the kindoms of Macedonia, Epirus, Pergamon, Bithynia, Pontos, and at a stretch, Egypt, eventually falling to either a rebellion by Celtic mercenaries, or expansionist Celtic states from Italy or the Balkans by the First Century CE. Tribal unions based in Gaul would have to eliminate their immediate rivals before expanding outward.
Religion throughout this area would probably resemble that of the Scordisii in your Sweboz TL, but on a greatly expanded scale, with priests proseltyzing among the Jews, Dacians and Germanics, bringing the area into a sort of religious unity, which combined with competition between medium-large scale states could lead to very fast discoveries and dissemination of ideas. Hm, a sort of European Hinduism, if you will, a polytheistic religion with an organized structure and great local variation, although likely lacking such a firm caste system.
I reckon the Scordisci and the Galatians may have had their own equivelant to the Druid Caste, so if they stepped up their game in a Rome-less ATL, we could see some serious developments in theology and religious practice. But competition may occur from the Thraco-Dacian cult of Zalmoxis, a sort of proto-Monotheism native to eastern Europe.
I think before there is a chance of Jewish conversion to European Celtic Polytheism, the Temple would have to be destroyed. The Diaspora Jews used the Oral Torah, so they would likely diverge into seperate fringe-cults, or would gradually forget their heritage and assimilate with the dominant culture.
Linguistically, the Celtic languages, specifically the Gaulish parent to the languages in Gaul, Italy, the Balkans and Galatia, will eventually diverge a la Vulgar Latin into the Romance languages. Iberia, Britain and Ireland will be a bit different, provided they stay out of the Gaulish zone of conquest. Iberia, in particular, could go a few different ways, Punic, Celtic, Celtiberian, Iberian, probably one or two others I'm forgetting.
Unless Carthage's ruling elite is replaced by ambitious military strongmen, it will soon be conquered by new dynamic empires from the northern Mediterranean, or subsumed by the increasingly unified and Punicized native Libyan kingdoms, such as Numidia.
Spain could be unified eventually by the Lusitani or the Celtiberian Arevaci, or be conquered over time by a united Gaul.
So, I'm seeing a Helleno-Gaulish cultural fusion more or less dominant in the European-Mediterranean region, with some very strong local variation in Egypt and Syria, and slightly less strong in Germania, Dacia, Spain, the Isles and North Africa. This, however, basically hinges on little further expansion, and assumes that these states don't tend towards a large-scale political unity. If some Celtic Empire does result, with the same assimilationist tendencies as Rome, well, Egypt would remain distinctive, linguistically and religiously, but otherwise, much more uniformity.
I envision that a Scordisci-Boii-Volcae alliance topples Macedonia, establishes a new kindom as far south as Thessaly, and exacts tribute from the Greek city-states after repeated military raids and sackings.
The Davas (fortified cities) of Dacia could oppose Celtic dominance in the Balkans, and use the Cult of Zalmoxis as a unifying ideology.
Continued reliance on mercenaries due to frequent wars with the Seleucids may make Ptolemaic Egypt prone to uprisings by either native Egyptians or dissatisfied soldiers. Sizable contingents of Gallic or Galatian warriors could band together, and seize key cities along the Nile. A successful Celtic takeover could see the new ruler adopt the the title of Pharoah, seek the support of the native priesthoods, and assimilate gradually into the Hellenized populace.
The British Celtic tribes could gradually form into larger polities, or be subsumed by a growing Gallic empire. When it comes to this ATL's version of the Viking Age, it would be interesting to see how far the large ships of the Gallic Venetii tribe would be improved upon. Settlement in Iceland could could occur earlier by the Irish. Maybe further trips may take them as far as North America.
Germania could become another target of Gallic colonization, or completely adopt Celtic culture as their own. Some tribes, the Belgae, Helveti and the Treveri may have been Germanic in origin.
Also, a form of democracy may well be adopted by most of these states, Celtic and Athenian practices mesh well in this area.
Some Celtic tribes practiced a republican form of government (the Aedui). If the Celts come to dominate in Greece, they may leave the governmental structures of the individual Greek city-states intact, provided they recognize them as their overlords, and pay them tribute. Down the centuries Greek-style temple compounds could be administered by a professional priestly class descended or derived from the Druids. The Oracles could be used by Hellenic Druids as a way of interpreting the Will of the Gods.
I'm really liking this idea, by the way, don't remember if I said that already.
Glad you like it.
