Apparently that's not true. From what I've heard, Americans generally leave their shoes on at home. I would see this practice on American television programs and think they're leaving their shoes on because it's TV. That's not true. Most Americans leave their shoes on indoors.
Canadians do not. In fact, only under very strange circumstances would a Canadian leave his or her shoes on in a house.
It's probably because Canadians are a very polite people. They don't want to cause a fuss. They don't want to draw attention to themselves. They don't want to make a mess. And so the shoes come off.
It doesn't matter how clean the home is, Canadians are removing their shoes unless explicitly told otherwise. I've been to vacant apartments and taken my shoes off at the door. It's just second nature now.
Of course, I also say sorry when someone bumps into me. Even when they're completely at fault and I did nothing wrong I'm still going to apologize. It's the Canadian way.
An easy way to spot a Canadian is to bring them into your home. Yes, I understand that inviting a Canadian into your home is a dangerous action. Because of this you should attempt all other forms of Canadian identification before trying this step. Once you allow a Canadian into your home you will find that they will fill your fridge with Canadian beer, turn your TV to a hockey game and crank the air conditioning to make it colder. That's just how Canadians are.
However, if you do decide to invite a suspected Canadian over, you will immediately know if they are truly Canadian or not. It will be evident within 30 seconds. A real Canadian would not think of leaving their shoes on when they're in your house. A real Canadian would also not think of locking the front door behind them, so you will need to do so once the Canadian is safely inside. Canadians do not lock doors because there is no such thing as crime in Canada.