I wouldn't say it's a general belief, but it is a point that certain groups like to push. See e.g. https://www.economist.com/leaders/2026/01/28/haters-on-the-r... (paywalled, but even the first paragraph is enough).
replyDonald Trump and Farage say so? Must be true.
replyWhere is the evidence that it is a peculiarly American belief? Or were you just eager to pick on Americans