You don't have to be a US company to get a .us domain. Under the so-called Nexus rules .us domains are available to anybody who fulfills the requirement of being
A foreign entity or organization that has a bona fide presence in the United States of America or any of its possessions or territories.
The rules go on to say
Prospective Registrants will certify that they have a “bona fide presence in the United States” on the basis of real and substantial lawful contacts with, or lawful activities in, the United States of America.
I read this to mean that you qualify if you are a foreign company that sells goods in the United States, or if you are a foreign club or similar that has members in the United States. You don't have to be based there.
The fact that Register.com (the registrar) have put themselves down as billing and technical contact is of no relevance at all - and neither is the fact that they put the address of their operations centre in Yarmouth NS instead of their head office in New York NY!