Bret Devereaux

So, 1) Gibbon is hardly the last word and 2) all of those places are in Italy but 3) the auxilia @SarahEBond is talking about comes from mostly outside of Italy and 4) were often recruited so that the legion could be supported by combat styles Italy lacked (archer, horse archer)

The Roman Empire produced cultural convergence outside of Italy, but unevenly. It is not clear that the Romans themselves ever intended to do so, but it became on of their great strengths: getting people of other cultures to buy into Rome.

The examples I love to use when I teach are second century mummy portraits from Egypt - Egyptians often freely mixing their own styles with dress that marks them as Roman citizens. E.g. https://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=119830&partId=1&searchText=Fayum+mummy+portraits&page=1 …