Regardless of who owned the local loop or who sold service on it, US local loop lengths are longer than most other countries (regardless of population density).
I believe the long local loops relates to a massive central office "centralization" in the US when digital switching came along. Why exactly this centralization did not happen in Europe (and Australia) is not clear to me, it might have involved timing of DSS deployment versus the timing of DSL practicality.
The result is that the US has fewer COs, and longer local loops. Worked fine for voice, not so well for DSL.