The RIRs each have a geographic monopoly and at their creation, this is required by ICP-2 (the original). This has nothing to do with where you land on any of your subsequent questions.
Are the European Union or African Union, geographic monopolies?
The NRO cartel has agreed to specific territories served by each RIR, granting each a geographic monopoly.
You write as if a couple of guys formed an organization and decided how the system must work.
FWIW, the RIRs (NRO) are an outcome of wider internet community engagents that lasted years if not decade for which you historically particpated in as a member of the said communities. Most of the rules of engagent were decided through wider consultations at policy debates and some by those elected by various internet communities.
Do not confuse the RIR/NRO system with the pseudo-private enterprises operated by sole propriators who believe that they can change a system that has served the public so well for decades and continue to do so.
Because organizations served by RIRs are not constrained by those boundaries, many operate in more than one region and the rules get fuzzy, but in general, territorial exclusivity is long established.
And countries do have some embassies in different other countries.
I’m not saying this is good or bad. I see benefits to it, but I also see reasons it might be better to phase it out.
In any case, it might be worth considering granting a certain right of a registrant to transfer the servicing of their registration to the RIR of their choosing.
Each region has its own rules of engagement. When such registrant decides to play in a certain service region, they must comply with existing rules of the game in the said region.
Noah