ICANN policy is very different for country code TLD and generic TLD. Every country (with minor exceptions) decide over their own TLD and thus decide whatever rules they want. It is explicitly a hands off approach in their management of the TLD's.

Generic TLD are different. ICANN dictate to different degree each generic TLD, and is also the one that give accreditation to registrars. ICANN has given different companies the role of operating and handling databases and registration systems, like Verisign with .com, but it is still ICANN that dictate policy. ICANN could decide tomorrow that Verisign is no longer suitable to run the operation of generic TLD's and thus move it to a company located in a different country.

Moving the operations of generic domains to a less US-centric location is not a new idea, same with the legal locations of the organizations that are ICANN and IANA. As I understand it, they are mostly located in USA as a matter of history.