Ummm, no. RIPE-NCC and APNIC also assign address space as regional registries, CANET, JPNIC, KRNIC, and AUNIC/Telstra assign space as national registries. One might claim the IANA has the ultimate responsibility regarding address space, but this is somewhat irrelevant to this discussion.

A minor clarification: CANET does not run the Canadian IP registry; it is run by the University of Toronto. CANET does run a route registry for CANET customers.