I will be using the camera on a tour of USA, Canada and Alaska.

If you are not filming you could go for 550D as which be cheaper. With Canon you get a better ISO range as the Sony uses the Translucent technology which darkens the amount of light coming into the camera and aint good to shoot at night.

But also there are superzooms out there which probably bet much better for tourist photography as you dont have to change lenses if you want to zoom in very far. As the Canon sx40 has a range of 24-840mm which be very enough to shoot anything and you dont have to change the lens to miss any action.

Panasonic is going to release a new superzoom soon called Lumix FZ200 with 25-600mm but will be f2.8 all the way making sure it bright enough the full range of the zoom which not much has. Even if you buy those DSLR with kitlens they wont be f2.8 that bright and full range but f3.5 at range of 18mm and zoom in to 50mm it becomes f5.6 and loses allot of light.

If u r traveling u gonna love the gps on the camera, else it has much faster frames per second that can mean taking a good picture or just missing it. It should be much lighter as well. U gonna save some money at front and when u get new lens as well. Best auto focus than most cameras. U can have great fun with the panorama function, remember u may not always have space to move back and take the whole shot or have a edge distorting wide lens. I hope this helps. 

Look at DxOMark, they compare Cameras in a very professional way. At DxOMark the Sony Wins... buy the sony. Sony is also the manufactor for the Nikon Sensors... it cant be wrong i think. Look here 

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/692%7C0/(brand)/Canon/(appareil2)/675%7C0/(brand2)/Sony

Canon 550D or 650D if you can afford... Your photography and videography needs will be well satisfied with both of them. Since you want a tourist camera, buy a 550D and a telescopic lens!!

Go with the Sony A=57. As a successor to the A-55, it beats the hell out of Canon 600D