The centennial of this holiday passed by nearly two weeks back. In recognition and celebration of the friendship and cooperation between the British and the American peoples, in the U.S. and in Canada December 7th, 1918 was variously proclaimed by governors and mayors as “Britain’s Day”, “Great Britain’s Day” or “British Day”, with keynote ceremonies in New York, Washington and Montreal. King George V, French Prime Minister Clemenceau, President Wilson (who was in France) and many other leaders and personages sent messages of support.  

Apparently this was a one-off, as there are no reports of the day being observed in succeeding years. Of course, future events would ensure that Americans would long remember the day for an entirely different reason.
You can read about the observance held in Pittsburgh, PA here.

You can read an Australian account of the occasion here.

James (“Jim”) Patton BS BA MPA is a retired state official living in Shawnee, Kansas and a frequent contributor to several WW1 e-publications, including "Roads to the Great War," "St. Mihiel Tripwire," "Over the Top" and "Medicine in the First World War." He has spent many hours walking the WW1 battlefields, and is also an authority on British regiments and a collector of their badges. An Army Engineer during the Vietnam War, he does work for the US World War 1 Centennial Commission and has memberships in the WW1 Historical Association, the Western Front Association, the Indian Military Historical Society and the Salonika Campaign Society.