I would say low xx at best. With content/development, it could be used without too much trouble and people here in the US don't seem to mind the US extension as much as some of the others... even though it has nowhere near the clout of .com... But, the extension still does not normally have a whole lot of value.
It may be a cheap advertising trick, but I have almost all my .us sites up in red/white/blue. You may think I'm crazy, but I've noticed higher conversion rates on these sites than on almost all my others... Odd how the mind works.