According to the Canada 2006 Census, 316,350 Canadians reported American as being their ethnicity, at least partially. There are also between 900,000 and 2 million Americans living in Canada, either as full-time or part-time residents. [1]
According to U.S. Census estimates the number of Canadian residents was around 640,000 in 2000. [2]
According to Stats Canada, the trend has reversed over time as the absolute number of Canadians living in the US peaked in 1930 at 1.3MM, which would be about 12% of the Canadian population at the time, down to a current 1.8% [3] On the other hand, Americans in Canada acount for 0.66%. At most it's a 3X discrepancy, not 10X, and it's largely due to the draw of the US economy. What would be more interesting to me, IMO, would be how many return home.
By all means, have at them windmills though, at least you've got a good view from on top that high horse ;)
[1] https://en.wikipedia.org/wiki/American_Canadians
[2] https://en.wikipedia.org/wiki/Canadian_Americans
[3] https://www150.statcan.gc.ca/n1/pub/11-008-x/2010002/article...