The fact that house price growth in Canada generally appears to be significantly more than those in the US in the last few years does not mean that there aren't certain cities in the US were house prices are well beyond what is considered average either in US or Canada.
There are always certain segments of a market where prices are so abnormal that some might exclude such markets when trying to determine general market average to avoid skewing the data.
According to Zillow for instance, average home values in Los Altos CA is $2.6 million yet average household income in Los Altos CA is $154,000.
Trying to get get a $2.6million mortgage with a $154K income may be somewhat problematic. So bankers are likely to be forced to try to generate creative ways of financing an unafforable mortgage which often isn't a sustainable solution and/or people are likely to move elsewhere.
Apparently house values also increased by some 21% in Los Altos from last year according to Zillow which certainly isn't the national norm nor am I aware of traditional income growth being in that range here.