Why Invade Canada?
It's been done before. (And we're not just talking about those South Park kids or John Candy.)
You know if it wasn't for Benedict Arnold (Yup, the traitor of later) losing a key battle in the Revolutionary War, Canada would probably be a part of the U.S. (But much like New Jersey, we probably wouldn't want it).
Canada Has Stuff!
First off, let's make Alaska actually connected to the U.S. again! Those Alaskan folks are always getting screwed by not being part of the "continental 48 states". Let's give them a nice little bridge downstairs. A little bit of farmland never hurt anything either, but forget the permafrost part. Canada is the second largest country in the world, let's fix that.
If Christmas ever fails to come, the Canucks did it. The magnetic north pole is within the Canadian border. We must protect Santa Claus!
They're just a little too proud. Perhaps if they didn't think it was so cool to live in "Diet America" we wouldn't need to invade them, but with people like this guy and these people thinking that Canada is the coolest thing since sliced bread, we need to do our part to keep them in their place. There's a reason the continent is called "North America" and not "North Canada".
They stole our basketball teams. Since when does the "N.B.A." stand for "Canadians Can Play Too". We need to get Vancouver and Toronto annexed into America to preserve the "N".
They don't play nicely with each other. There has been a secessionist movement for years. Quebec doesn't like other Canadians, and the feeling is pretty much mutual. We don't have that in the U.S... you know, there aren't any (Texas) big states (Texas) that think that they're better (Texas) than the rest of the Union (Texas).
There's more, with links and such.