Is American flour different from Canadian flour?
You are very observant and are quite right to note that our Canadian baking recipes do not mix very well with some American flours, particularly those made in the southern United States. Why? Southern flour contains less protein than Canadian flour and does not absorb liquid as well. Avoid brands like Martha White and White Lily when making your Canadian recipes. They contain about 9%-10% protein. Look for unbleached all-purpose flour instead, a brand like Gold Medal, Pillsbury or King Arthur, that contains about 12%-13% protein, the equivalent of all-purpose Canadian flour.