In addition to .us.com, CentralNic has:
.EU.COM, .BR.COM, .CN.COM, .DE.COM, .HU.COM, .NO.COM, .QC.COM, .RU.COM, .SA.COM, .SE.COM, .SE.NET, .UK.COM, .UK.NET, .UY.COM & .ZA.COM
Many (some) companies have registered example-us.com in addition to their primary example.com domain.
They are not worth a thing now.
I suspect a couple engines actually devalue them, and for a couple others you don't need them anyway.
Thoughts?
I suspect a lawyer of some ability could seize the US.com domain, as one element of a damages award, IF he/she could show a pattern of the US.com operators countenancing "subdomain trading off" practices. Given the tenuous nature of their business model it would be in their best interest to vigorously policy against such "trading off" threats.
So, no, I see no need to protect your brand by such a registration, any more than I see a need to register your domain as a subdomain of millions of other domains.