Doing a quick and dirty search for 'Armored princess' on 'Video Games' category on eBay.com bring about 20 results (make sure you also choose 'worldwide') of sellers shipping it to the USA, most are brand new, so I guess there is no excuse, if you really want it then you'll get it by any means possible...
Don't wait for it to be on sale in retail on the USA, it may never happen, like in Australia, it is impossible to find KB:TL and the sequel in any retail shop even after all this time, so don't hold your breath, import it like everyone else does these days, that's what the internet is for!
