Actually, estimates of the number of Americans living in Mexico are much higher than you've listed, with the most common estimate being between 1 and 1.25 million (BTW, your estimate for the number of Americans living in Canada is also very low; it's generally also estimated to be about 1 million). But the catch is that the Americans in Mexico live in many different places. The largest number, as shown in the graph on the attached website, live around Tijuana -- but in 2010 they only accounted for 6.4% of all Americans living in Mexico, which is about 64,000 at the 1 million estimate -- and which is only one-third the number of Americans in Vancouver. The next largest group is around Lake Chapala, and that is only about 41,000 in 2010. As you can see from the graph, there are 20 locations with at least 11,000 American residents, which is how the number of Americans in Mexico becomes so large despite not having any one location with an American expat community remotely close in size to Vancouver.