I get that riding with a backpack is uncomfortable, but how is it stupid from a commuting standpoint to the point where you're "Off balance"?
Yeah, if you let your backpack hang to your *** like a high-school kid, it could shift around when cornering, but how "off balance" could you realistically be where it effects riding in a straight line in Ontario?
Top boxes would be preferable, but it comes down to $$, and usually a few hundred dollars at that.
I have no idea where you're coming from in regards to the "North American look"... Who actually WANTS to ride with extra luggage...?
As for going down with a backpack... Please refer to the video posted of me going down with my backpack. A laptop would simply be crushed if the rider should land on it. Falling on the street, there are a lot more that you can collide with that can break your bones than whats in your luggage. (Unless you decide to carry sharp or small/hard objects - ie. screwdriver).
If the argument is contents breaking, having a backpack with a bungee net wont save it, carrying it in side cases wont save it, and the only option is a large enough top case.
So far every person I've seen go down with side-cases, had them crack and open up throwing things everywhere while going less than 40km/h...