The US Memorial stands by the Sauer near the pedestrian bridge and remembers American units that were stationed, fought, or passed through Diekirch and the surrounding area from September 1944 to February 1945. It is a modest monument, but the setting is exactly right: quiet, public, and part of an everyday riverside walk.
Visit it before or after the National Museum of Military History. The museum gives the detail; the memorial brings the story back into the town itself.