Source: http://www.gamefaqs.com/ds/636598-aliens-infestation/data (http://www.gamefaqs.com/ds/636598-aliens-infestation/data)
The US release date seems to be October 11 now instead of September.
We're already discussing it at the following thread: http://www.avpgalaxy.net/forum/index.php?topic=39598.msg1172744#msg1172744 (http://www.avpgalaxy.net/forum/index.php?topic=39598.msg1172744#msg1172744)
The US release date has been October 2011 since the very beginning. The announcement never mentioned it, but the official US site always had that release window.