Andrew kohut , director of the pew research center , called the breadth of the u . s . image problem surprising , attributing it in part to the united states ' status as the world ' s sole superpower 佩爾研究中心主任安德魯?科哈特認為美國全球形象下滑的普遍性令人意外,并認為部分原因是因為美國是世界上唯一的超級大國。