Canada is in a bad situation with Quebec wanting to become independent. If they do, the rest of the Canadian provinces could split up from Canada as well because of cultural differences, and power could fall into the wrong hands. Also, since Canada isn't ever involved in very many conflicts around the world, their resources aren't being used in the best ways possible to help the world. The USA is constantly solving wars, and could really use the extra resources. Our military is already the best in the world, and with the Canadian additions other countries wouldn't dare mess with us. Not to mention, it would be much easier to get oil from Alaska and protect them from Russian or Chinese paratrooper landings. There is also Annexationist groups in Canada who strongly support this idea, so it wouldn't be a forced invasion and annexation.