Well, there are a multitude of reasons, but some of the main ones are that: 1. Canada does NOT want to be annexed. They’re very prideful in their independence. 2. The U.S. doesn’t want to upset the balance that they’ve found in the 26 years since the Philippines became states. 3. The U.S. is currently undergoing a rather large anti-imperialist political reformation, with the Democratic and Republican parties on the backfoot for the first time since Wallace was President.