After thinking on it I may know why the Swiss weren’t fond of Americans, especially the Air Force. Most of the 70 bombings by the allies after 1943 were done by the Americans, including the 1944 bombing of Schaffhausen. Although some of these may be attributed to mistakes, some, such as the bombing of Schaffhausen are suspected to have been done out of retaliation (for Swiss Air Force shooting down and dogfighting USAAF invading Swiss airspace and collaboration with Germans). This belief was especially prevalent back then. So you can imagine the Swiss were not very happy with these men.