There is no federal tax on food. States can, but not all do. I've never lived in a state that does, other than some that tax "prepared food" (restaurants) vs. just "food" (grocery stores).
There's no federal sales tax, but there are a host of tariffs on imports and regulations on what foreign merchandise can be sold domestically.
We can't, for instance, buy sugar from Cuba or beef from Mexico. Some of these rules are precautionary (prevention of the spread of foot & mouth) while others are purely political (sanctioning a country's economy to force a policy reform).
But they all result in higher food costs at home, to the benefit of the domestic agricultural industry.
Where I live (not the US) most food isn't taxed unless it's something that's considered more of a luxury item or has punitive taxes like soft drinks with a sugar tax.