Since 1998, an organization called the Internet Corporation for Assigned Names and Numbers has overseen the directories, mostly by setting rules and creating mechanisms for settling disputes. But ICANN also has a boss at the U.S. Commerce Department.

It's a historical arrangement stemming from U.S. funding for the internet's early development. The domain name system we're familiar with was invented by the US and dates back to 1984, long before "Pokemon Go" or even came along.
The internet relies on an addressing system called the domain name system, or DNS, which includes directories that help route data like email and web requests where it needs to go. And someone needs to run the DNS.

Communications, air travel, utilities, shopping and financial transactions are now totally dependent on the internet.

Virtually everything run by the UN is rife with corruption. Why give them internet control?