As a Canadian what I understand, and I use to know the exact numbers, but the US does subsidize US agriculture. Canada subsidizes at approximately twice the rate as US subsidies. Europe might be 3 to 4 times US subsidies. And Japan subsidizes at some insane rates. Rice is at 800 percent or something like that.
Canada also does what is neatly calls supply management, which is just another word for enforcing egg, milk and cheese fixes on production levels.
You’re missing the most important US subsidy to agriculture which comes in the form of allowing illegal aliens from Mexico and Central America to work on farms for illegally low wages.
Canada should protest this subsidy immediately.
(No, I won’t be holding my breath)