Arbitrary JSON keys with Aeson - Haskell

I have a bunch of nested JSON objects with arbitrary keys.

{
    "A": {
        "B": {
            "C": "hello"

        }
    }

}

Where A, B, C are unknown ahead of time. Each of those three could also have siblings.

I'm wondering if there is a way to parse this into a custom type with Aeson in some elegant way. What I have been doing is loading it into an Aeson Object.

How would you go about implementing the FromJSON for this kind of JSON object?

Thanks!

Edit:

{
    "USA": {
        "California": {
            "San Francisco": "Some text"
        }
    },
    "Canada": {
        ...
    }
}

This should compile to CountryDatabase where...

type City            = Map String String
type Country         = Map String City
type CountryDatabase = Map String Country