Answer: Easy (i forgot to do Greenland but its an easy fix...)
Explanation: Since I live in the US I would first start taking over Canada during the spring, of course Canada's allies would help them but they wouldn't be able to deliver anything, because of United States Navy. It will probably be a few months before Canada would fully surrender from lack of food, and ammo. I would have the army keep control of Canada while the Military heading to Mexico in the end of fall. Mexico would be more difficult however their lack of supplies would be there demise as well, because the Navy and military would have surrounded them. I would go with the same strategy in South America, and ounce they were taken over id have the Military keep them under control. It be about a decade before I continued to Asia, to regain many more soldiers, now taking over China would be difficult indeed but since id still be allied with Japan for a deal of them keeping China's land, for they would have to agree the US was 10 times there size. After years wed finally take over Asa, ounce again id wait about a decade before I advanced while fending off Europe, because they understand that there next. Finally id surround Europe with the Navy and Military, and after taking down the last of there army id make Japan go under my rule.