You may have missed this, but the US dollar has been fairly weak for the past 6 or 7 years. The US, Canadian, and Australian dollar have been flirting with parity for a good number of years. Comparisons that account for exchange rates show that Canadians are frequently paying 20% more for identical products. Yes, there are other factors to consider. Yet even blaming things like taxes can be misleading since there is so much regional variation in the US.

So yes, we should probably be taking more care when making these comparisons. But no, it doesn't blow the entire argument out of the water.