There is not a specific antonym for diaspora, but the opposite of a diaspora would be the regrouping of a community or the coming together of a community. It could also be a renewal of a specific cultural group or ethnicity coming back together in a sort of revival of their culture.
The Eastern half of the Roman empire became known as the Byzantine empire. Haha and this is ironic because this is what I am studying in school now
contributed to American neutrality in the early years of World War II
