Ford definitely owns by far the commercial light/light-medium duty (class 2, 3, 4, 5) truck market. In medium/medium-heavy (classes 6 and 7), it's all about International and Freightliner.
Around here, private owner light trucks (classes 1, 2, 3) are about equally divided between the 3 US brands. Nissan and Toyota barely make a dent in that market around here.