I remember I had beach.santa-cruz.ca.us at one point registered to me. I owned beach.santa-cruz.ca.us, someone else owned santa-cruz.ca.us, yet someone else owned ca.us, and I believe Network Solutions took care of .us at the time.

You say "registered" to you as though this was via an official registrar but surely you mean that someone rented ca.us and decided on their own to lease out subdomains to people?

(Aside, I always see "owned" and "bought" but you can only ever "lease" under the ICANN system as the present situation so clearly demonstrates.)