I want to register a .us Domain name. what is criteria to find .us extension

The U.S. Nexus Requirement ensures that only individuals or organizations that have a substantive connection to the United States can register .us domain names

To qualify, you must meet the following criterion.
1.A natural person (i) who is a citizen or permanent resident of the United States of America.
2.An entity or organization that is incorporated within U.S. states.
3.An entity or organization (including a federal, state, or local government of the United States, or a political subdivision thereof) that has a bona fide presence in the United States.

no one really does care aboutt he rules in registering US domains, because like Namepros, no rules applied when i registered a US domain there.

No one cares about the rules!
Neither registrars nor the registry, simply because it brings them money.

i had one .us domain but before buyng i dont know this rules.

theres nothing like that but its very easy to own.

If you really want a .us name, you just go to a US register & reg it.