I think its good to diversify, and the .us ext can very well take off with the success of one. I am always happy when there is a big sale on Sedo, especially in the wake of .mobi.
In the meantime I try to visualize how a particular word may lend itself to a developed site that connects to the US in some way. I saw apprentices on your list (thanks Lasher) and noticed apprentices, which was gone when I checked;-(
Seems lilke a better chice then elbows for example of a name that connects well. Unless you wanted to do a silly site on elbows like; guess whose famous elbow this is?
Double names can also work when a more generic name is taken in that extention. Though I have yet to embark on developing, imagine that name developed in some way.--with a bit of seo and LP your good to go.
