In a scenario where the celts are prevented from entering the po valley, (perhaps by a combined effort of Etruscan cities) how would this affect the development of the region, and where would these tribes migrate to instead?
We do not know if Ligurians were ever a real ethno-linguistic group, not only is the name apparently a Greek exonym, we also have no Ligurian inscriptions.It's either the Venetics, Etruscans or (ancient) Ligurians who'd fill the gap.
Does Rome remain just a regional power, absent the sack?