Does anyone have advice for learning what the communities of interest in a state are?

[Хahar 🤔]

In a lot of cities especially, COIs will mirror sharp political divides. NYC is a prime example of this.

As is often the case, New York City is a poor example because it is unlike other American cities. Most American cities do not have Republican areas: there is not a single Republican precinct with more than ten votes in Boston or St. Louis or Minneapolis or Seattle. In the whole city of Los Angeles in 2020 there were exactly two.