I have registered a new domain, kundanchhabra.us, and have updated the nameservers to be ns1.dreamhost.com, ns2.dreamhost.com and ns3.dreamhost.com. This information has already propagated as seen by http://www.whois.sc/kundanchhabra.us
And I can also check on dnsstuff.com, to see that my nameservers are indeed ns[1-3].dreamhost.com. The website dnsstuff.com reports that the name servers failed. This is funny because, I have other domains using DH nameservers. They work fine. So what's different about a .us domain name?