On D-Day itself, US forces were actually in the minority. James Holland starts his article D-Day: Exploding the myths of the Normandy landings with "MYTH: D-Day was predominantly an American operation (...) Rather, it was an Allied effort with, if anything, Britain taking the lead." I'm not sure where some of his numbers come from (e.g. two thirds of aircraft and troops being British seems a slight over-estimation), but the broad thrust is accurate. Looking at a variety of other sources (Operation Neptune: The Normandy Invasion D-Day 6 June 1944 from the Naval Historical Branch; US Naval Administrative History of World War II Volume V: The Invasion of Normandy; The Royal Air Force 1939-145 Volume III: The Fight Is Won) gives figures of 132,815 troops landed from ships; of those over half (75,215) were British and Canadian (plus a smattering of others, e.g. Free French). Three divisions were also landed by air, 2 US and 1 British. Of 14,674 air sorties on 6th June over a third (5,656) were from RAF Commands (including Canadian, Australian, New Zealand, Norwegian and Free French squadrons). Of 6,483 ships, less than a third were American; the majority were British, plus a substantial Canadian presence, and smaller numbers of Free French, Polish, Norwegian and Dutch vessels.

/u/thefourthmaninaboat wrote an excellent post about the fighting on the Anglo-Canadian beaches, in addition to many other fine posts about (primarily) the naval aspects of D-Day.