In the US, there is a consumer magazine Consumer Reports. This magazine is published by a non-profit who takes no advertising dollars and pays full price for anything they review so as to avoid any appearance of bias. Every year, CR sends out a survey to all of its members (8 million+) about the cars that they own, asking specific questions about problems & repairs their cars have had over the last year. They aggregate this data and present it as reliability ratings. In the past, Japanese cars have had overwhelmingly better reliability ratings than US cars. I recall in the late 90s / early 00s US cars rarely did better than the middle value of their 5 bubble scale for overall reliability, while Japanese cars almost always got the top value. (German cars also rated highly for reliability as well, but are much more expensive in the US than Japanese imports)
The difference may no longer be as large or uniform, but this is certainly where the generalized view came from.