Mr Ross was on BNN and explained that the US was trying to improve the current US $500 billion dollar trade deficit...which to me sounded reasonable. He  was also pointing out that non-deductible VAT taxes (ie HST/GST) were an issue for US exporters. (the US has no VAT tax).He did mention that Canada was not at the top of the list. Other countries like China, Japan, Germany, South Korea and Mexico were.
The way I interpreted his comments... A US exporter has to price in his profit + the HST/GST selling into Canada. (more costly)
For a Canadian Company exporting into the US...it needs to price in their profit only, making their products less expensive because the US has no VAT or HST equivalent. 
For Mexico say car companies, China may supply 30% of a cars parts into Mexico, and when the car is sold into the US VAT free....China thus evades import taxes. The tax issue will be more of an issue for the provinces (if they have an HST) and the Feds GST.