So here is my strategy for a diplomatic victory with Canada. In the beginning of the game build a couple scouts and try to meet as many city states before anybody else, that way you get free envoys. Then adopt the government Monarchy which gives you a bonus to envoys and get envoys sent out to as many city states as picking the city states that other civs are ignoring, the idea is to become suzerain of as many city states as possible to boost your diplomatic favour per turn. Then protect your city states with an advanced army. In this video Persia declares war on Zanzibar and since I had no military to speak of I leveraged two city states units, upgraded them and then used them to fend off the Persian assault. Make alliances with as many civs as possible and try to fulfill their agendas to gain their friendship and loyalty. Once the modern era hits the idea is you have saved up your diplomatic favour to vote for yourself to get diplomatic victory points. Concentrate your diplomatic favour on getting diplomatic victory points, the other resolutions are not that important. By the end of the game nobody will vote for you when you have 9 diplomatic victory points, so you have to get your final victory point through disaster aid relief or winning a scored competition like being the greenest civ in the game only using renewable energy. Finally build giant death robots to protect weak nations and city states. That is my general overall strategy and it worked, try it out next time you play canada!