The ability to propagate the politics depends mightily on the success of the community though. It’s sort of the other side of the ‘brain drain’ principle-- if people have to leave the community for educational or economic opportunity, they’re probably not going to be able to reconstruct the same echo chambers.
Even when you see a preserved group within a larger population (think of Chinatowns and Little Italies), they’re inherently getting a lot more cultural exchange than back in the home country.
A lot of the most self-destructive policies (neglecting education, running the environment into the ground, skate-where-the-puck-was-in-1972 economic policy) are just begging for decades of brain drain. The kids are going to leave because there’s simply nothing there but the Gizzard Extraction Plant, and that got automated in 2032.