well said @Sam,
the unpopularity and what makes it worthless is that the AMERICAN Companies don't give a c*ap about it. Everyone in the us goes for .com there for .us is .useless ...
If you look at other companies of other countries (england, germany, france, spain, holland, etc..) they always prefer their own ccTLD and use the .com version for international purpose (not just for english)..
Hell, even .com US Companies use other countries' ccTLDs, no one in germany uses google.com, they use google.de and other countries do the same... whereas usa uses google.com and not google.us .. .us won't be established as .de .co.uk .nl .fr etc... why? cause not even the gov cares about it, in europe or elsewhere the govs use .gov.cctld or directly the cctld. but in the us the directly use .gov .edu .mil etc..
every german govermental site uses .de ... universities use uni-"city".de etc.. the .US ccTLD would have become a major cctld if the gov would support it, there a few gov sites on us as far as i could see. states use them with their state codes, NY.us but nothing more. if the gov would have used .us as second level that would made a mayor influence on ppl seeing the .us cctld being used properl. mil.us gov.us edu.us etc... but well, .us will never bea big player..