Is cookie a blanket term for all types of biscuit in America?
I believe so. We also may use “cracker”, too.
I’ve never used the word cracker to refer to anything but those dry, brittle, salted things you put cheese on. Saltines, Ritz, that sort of thing.
For me cookie is a blanket term for all types of sweet biscuit (UK definition). US biscuits, however, refer to a non-sweet, scone-like baked good eaten with breakfast, usually with butter, jam, or gravy on it.
Waiting for Winter 