Culture, simplistically, is a derivation of what we believe and how we think and act, which in turn are derivations of the information we are exposed to.
In the past, information was limited by geography to a large extent. Local newspapers, leaders, and intellectuals. With the Internet, it is not. You can have different information exposures and consequently, different cultures, between neighbors. You can find polarization within a street, rather than just between states, countries, or continents.
This has interesting implications for governance, which is still geography-based. Governance, which is simplistically what strategy and policies should we collectively follow, largely derives from culture. If culture is no longer geographic, how can we govern geographically?
While this is short-term problematic, I think it is long-term positive as it unlocks a degree of freedom for people - to align themselves with whichever belief and culture they prefer. We still exist in the physical world and not just on the internet, so local cooperation is still essential. Eventually, governance will have to reduce to simply matters of local infrastructure and utilities, like roads, safety, and taxes, and not matters of morals. This philosophy is already reflected to some extent in the Federal-State split, but would probably lean further to Federal-State-Person. But the lines are blurry and most decisions are going to continue to be contentious.