Yes, some Canadian grain did make it to the US during your time period. Most of it via lake boat to places like Buffalo. Canadian imports were often driven by shortages of US grain as a result of drought or other crop problems in the US. I believe the two most common grains imported were barley (for malting...beer) and specialty wheat like durum (for milling into semolina flour for pasta).
During the period of prohibition in the US there was a marked uptick in imports of single carlots of Canadian grain. I have talked to old timers in the US grain trade who would tell stories of having their buddies at terminal elevators in Canada load a hundred or so cases of Canadian liquor in the ends of the car and then load the bulk grain completely covering the contraband. When the car got to its US destination it was usually set aside and unloaded by "management" on weekends when the bulk of the elevator employees were off.
