Canadian English is not a different language, just different spelling. If you are going by accents, accents vary even in a tiny country like the UK. Here in the US, someone from Boston sounds vastly different from someone in Dallas, for example. Kinect uses the Xbox 360, so it makes sense it will use the region the system is from.
Besides, voice control in Kinect was only confirmed recently anyways. The main draw was navigating through motions. I won't be getting Kinect, but only because it's not worth $150 +tax (so $162 for me).