Not always. You are allowed to use reasonable force, whatever force is required in order to remove the threat from your home. If the intruder is not armed, you cannot shoot him/her. If the intruder is armed and you have reason to fear for your own or other family members lives, you can shoot the intruder, IF no other means would have stopped the threat.
When I was a security foreman I ran into these issues all the time, almost nightly actually. No matter how well trained guards were, some drunk concert or game attendee would start the excessive violence claims with police. Of course, with cameras everywhere, it was easy to prove either way. The trick is removal of the threat.
If someone comes at you with a knife and you grab it and stab him with it, you can face assault charges. If someone comes at you with a knife, you grab it and pin him to the ground, you are okay.
The key is grabbing the knife. Once you have it, he is unarmed and you have removed the threat.
So if some guy has a gun pointed at you, the American solution would be to shoot before he did. By Canadian law that would ALMOST be acceptable but not always due to grey area.
If some guy in Canada has a gun pointed at you and you can safely flee, you must do so, run like a little rabbit.
The castle doctrine in the US is becoming harder and harder to stand/hide behind. That's when you can shoot anyone on your property. There have been cases where the intruder fled the home and was shot while leaving. If he has his back to the shooter and is leaving, the Castle doctrine no longer applies and you are the assailant.
As more old school Americans die and a more aware generation grows older, there is greater support for more realistic measures than just shoot first and ask questions later. It's gonna take a few decade yet, but American society will come around to the mindset shared by other free nations one day. How bad it will be by then, I don't really know though.
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