Who cares if the average IQ is 1 point higher there than in the US?
Does the comparison control for demographic differences like cultural assimilation? First generation immigrants from poorer, less educated countries south of the US obviously explains some of the differences. We know this because of the list of countries at the bottom of the list where access to education helps explain lower IQ scores.
Mexico has an average IQ score 10 points lower than the US. Illegal immigrants migrating to the US probably have lower IQ scores than Mexicos average. Is it really that hard to explain why there might be a 1 point difference between the US and Canada?
Come to think of it, if we could filter out IQ scores from the first generation of illegal immigrants from both countries, we would expect to see that difference between the US and Canada suddenly appear equal or even reversed?