It all goes back to the fur trade--it worked better with central organization under conditions of peace, order, and good government, where personal safety depended primarily on strong trading alliances and with institutional/military solutions to conflicts. The ranching that formed the basis of the early United States was a much more decentralized, individual activity that spawned a belief in the merits of individual life, liberty, and the pursuit of happiness, where an individual and his gun were more or less the only thing protecting the homestead from bandits and varmints.
Our different histories have led to different laws and different attitudes around how violent conflict is to be resolved.
At any rate you certainly can defend your home from intruders in Canada. You can use whatever force is required either to arrest them and hold them for the police if they have committed a serious crime, or in other cases to evict them from your property forcibly.
Unlike in the United States, however, you are strictly limited to using the least amount of force possible under the circumstances.
The only point I am making is this really:
If you've got the intruder under your gun, and theirs is not pointed at you, so that you have the drop on them, under Canadian law you cannot shoot them. In that case you have the upper hand and you have certainly got a less violent alternative available--namely ordering them to freeze and drop their weapon. Similarly if they turn and run shooting them in the back is going to be frowned on--you had the option of letting the police deal with them later.
I am simply denying the claim made on this thread by multiple posters that as soon as someone is in your house with a gun you can shoot them. It's not true. In some cases it's true but in most cases there are less violent means available to you.