I've seen it happen before, myself, especially once nations get their initial targets in, and you start having excess influence bleeding everywhere. It's happened to me late game, when I've maxed out everyone I try to influence and then I randomly start having enough points to become cordial with a nation halfway around the globe. Regardless, it is a consideration, as the AI is sometimes weird. I find that Canada is actually easy enough to integrate, so it's better to keep them. Without any US cores, and if you keep US relations high, that takes an entire hemisphere of headaches away. Typically worth it.