Ok,you start with Canada.No one would ever suspect Canada.You take over Canada,totally in secret so the rest of the world has no idea.Then,once you're secure there,you use Canada as a base of operations to start on the rest of the world.Because Canada is so peaceful,the first place you attack won't see it coming.I'd go after Asia first,since they supply most of the world's technology.Then,when the rest of the world is reeling from surprise,and you've got Asia under your thumb,you go after the countries that supply the oil.If you cut off the tech,and the oil,and many other imports,then America would be weakened and you could go after them.Once you capture America,you're pretty much set to take the rest of the world...
I've put a little too much thought into this...